Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-08-12
2001-01-09
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S733000, C029S732000, C029S598000, C310S234000
Reexamination Certificate
active
06170146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotor used for a small motor, and more particularly to a method for assembling a rotor in a DC motor with a brush, which has a 4-6 (four magnet poles and six salient poles of the armature core) structure.
2. Related Art
Referring to
FIG. 8
, there is illustrated a rotor
100
of a small motor with a brush which has a 2-3 (2 magnetic poles -3 salient poles) structure. In the rotor
100
, an commutator unit
120
is provided with a armature core
101
and three commutator pieces
103
separated by slits
104
. The armature core
101
has three salient poles
102
radially extended therefrom. Coils (not shown) of different phases are wound around the salient poles
102
. The commutator unit
120
is tightly coupled to a shaft
107
. In this type of the motor, an exactness of the timing of switching the current feeding to the coils of the phases depends largely on an accuracy of the alignment of the center line P
1
of each salient pole
102
with the center line of the corresponding slit
104
. Therefore, a misalignment of those center lines degrades the switching timing exactness, and causes cogging and an increase of torque ripple.
In a conventional measure taken for securing an exact alignment of the center lines, positioning protrusions
106
formed on an commutator holder
105
are fit into recesses
109
formed near a shaft hole
108
of the armature core
101
.
In the DC motor of the 2-3 structure, the conventional measure secure secures an alignment accuracy to some degree. However, the following problem is inevitably created. The recesses
109
are excessively close to the center of the shaft hole
108
. As seen from
FIG. 9
showing the positioning protrusions
106
of the commutator holder
105
and the recesses
109
of the shaft hole
108
, minute dimensional errors arising from dimensional inaccuracy of each part and of the part-to-part are enlarged in the radial direction. Therefore, it is impossible to expect the alignment accuracy as designed, in practical use.
In the DC motor of the 4-6 structure or higher grade structure (the number of salient poles is larger), the slits
104
and the commutator pieces
103
are increased in number. Therefore, an angle of each curved commutator piece
103
is halved, and as a result, the contact area of each commutator piece
103
with the commutator holder
105
is reduced. As a result, the commutator pieces
103
is easily tiltable, and more strict requirements are put on the assembling accuracy of the commutator unit
120
and position accuracy of the salient poles
102
of the armature core
101
to the commutator unit
120
. In the DC motor of the 2-3 structure, a tolerable alignment (deviation angle) of the center line P
1
of the salient pole
102
to the center line P
2
of the slit
104
is 3° or smaller. In the DC motor of the 4-6 structure, it is 1.5° or smaller. Therefore, some adjustment is essential in manufacturing stage.
The terminals of the coils
110
wound on the salient poles
102
of the armature core
101
are connected to the armature risers
111
, and soldering is applied thereto by a soldering iron. In the soldering process, pressing force and heat by and from the soldering iron possibly deform (denoted as H) of the risers
111
and the commutator holder
105
, and degrade the roundness of the commutator pieces
103
. When the DC motor of the 2-3 structure is compared with the DC motor of the 4-6 structure, a larger number of solderings must be applied to the risers
111
in the latter motor, and much heat stays there since the soldering points are more densely located. The thermal deformation H is more intensive.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a rotor assembling method which can exactly position the salient poles of the armature core to the commutator unit and lessen the adverse effects by the soldering process to a minimum.
According to an aspect of the present invention, there is provided a rotor assembling method comprising the steps of:
forming a shaft hole at the center of an armature core with salient poles on which coils are wound and forming through-holes at positions apart from said shaft hole;
forming engaging portions in an commutator unit at positions corresponding to said through-holes of said armature core;
inserting a rotary shaft into and through said shaft hole of said armature core and fixing said rotary shaft therein; and
inserting positioning pins into said through-holes of said armature core from one side of said through-holes, and bringing said engaging portions into engagement with said positioning pins protruded above the other side of said through-holes so that said armature core is positioned relative to said commutator unit, and fixing said commutator unit into said shaft.
In the rotor assembling method of the invention, the through-holes of the armature core are aligned with the engaging portions by use of the positioning pins. The positioning of the armature core to the commutator unit is carried out in easy and quick manner. This leads to improvement of the motor characteristic.
In soldering for the connection of the coil terminals to the risers, the commutator holder and the risers are supported, from their underside, by the support tool. Therefore, the soldering may be carried out without the adverse effect of the heat and force by the soldering iron, viz., free from thermal deformation of the support tool and the risers, and crack of the quenching element by heat. The result is to provide efficient manufacturing and assembling.
REFERENCES:
patent: 4577399 (1986-03-01), Ott
patent: 4945631 (1990-08-01), Banner et al.
patent: 5325575 (1994-07-01), Ichikawa
patent: 5658477 (1997-08-01), Kerker et al.
patent: 60-102847 (1985-06-01), None
Katagiri Masayuki
Miyazawa Hiromi
Takei Hiromitsu
Kabushiki Kaisha Sankyo Seiki Seisakusho
Sughrue Mion Zinn Macpeak & Seas, PLLC
Trinh Minh
Young Lee
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