Miniature motor

A miniature motor having a motor case comprising a motor housing, fitted with a permanent magnet field and having an opening at one end thereof; an insulating brush base, made of a synthetic resin, fitted to the opening of the motor housing for holding brushgear; and a cover plate, made of a metallic member, covering the surface of the insulating brush base; the motor housing having a plurality of crimping pieces formed by notching the edge of the motor housing opening; the cover plate being fitted to the motor housing by engaging the cover plate with the motor housing opening, and bending and crimping the crimping pieces, characterized in that the cover plate has along the outer periphery thereof a plurality of recesses, which are concave toward the motor shaft, and the recesses are crimped by means of the crimping pieces so as to fixedly fit the cover plate to the motor housing.

BACKGROUND OF THE INVENTION 
This invention relates generally to a miniature motor, and more 
particularly to a miniature motor having such a construction that a cover 
plate is fixedly fitted to a motor housing by crimping the cover plate, 
which is engaged with the opening of the motor housing to the motor 
housing, by means of crimping pieces provided on the opening of the motor 
housing, and that recesses, which are concave toward the motor shaft, are 
provided along the outer periphery of the cover plate; and the recesses 
are crimped by means of the crimping pieces. 
DESCRIPTION OF THE PRIOR ART 
Conventionally, cover plates used in miniature motors are made of synthetic 
resin moldings. Such synthetic resin materials have drawbacks such as (i) 
vulnerability to heat, and (ii) proneness to distortion due to 
flexibility. To overcome these drawbacks, a cover plate comprising an 
insulating brush base, made of a synthetic resin, and a metallic member 
disposed on and fixedly fitted to the insulating brush base by means of a 
fixing means, such as crimping or integral molding has been conceived. As 
shown in FIG. 3, a cover plate 1 is engaged with and crimped to the 
opening of a motor housing 2 by means of a plurality of crimping pieces 3 
provided on the opening of the motor housing 2. In the figure, numeral 4 
indicates a metallic member, as described above. 
In the conventional type of miniature motor, the cover plate 1 is engaged 
with and crimped to the motor housing 2 in the direction of motor rotation 
by the crimping force of the crimping pieces 3. This could result in the 
unwanted rotation of the cover plate 1 with respect to the motor housing 2 
in the opposite direction of motor rotation, particularly when the load 
fluctuates. Furthermore, it is difficult to position the cover plate 1 on 
the motor housing 2. Another problem is that dirt and dust tend to enter 
the motor inside through gaps between the cover plate 1 and the motor 
housing 2 at the crimped positions. 
SUMMARY OF THE INVENTION 
This invention is intended to overcome the above discussed problems. To 
accomplish this, the miniature motor of this invention has a motor housing 
fitted with a permanent magnet field and having an opening at one end 
thereof, an insulating brush base, made of a synthetic resin, fitted to 
the motor housing opening for holding brushgear, and a cover plate, made 
of a metallic member, covering the surface of the insulating brush base; 
the motor housing having a plurality of crimping pieces formed by notching 
the edge of the motor housing opening; the cover plate being fixedly 
fitted to the motor housing by engaging with and crimping to the opening 
of the motor housing by bending and crimping the crimping pieces, and has 
such a construction that the cover plate has along the outer periphery 
thereof a plurality of recesses, which are concave toward the motor shaft, 
and is fixedly fitted to the motor housing by crimping the recesses by 
means of the crimping pieces. 
These and other objects and advantages of this invention will become 
apparent from the following description taken in connection with the 
accompanying FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE EMBODIMENT 
FIG. 1 is a perspective view illustrating a miniature motor embodying this 
invention. In the following, the embodiment shown in FIG. 1 will be 
described, with reference to FIG. 2 which is an exploded view of the 
embodiment shown in FIG. 1. 
In FIGS. 1 and 2, reference numeral 1 refers to a cover plate or cover 
member; 2 to a miniature motor housing formed of a cylindrical housing 
wall 22; 3 to a crimping piece including side portions 23 disconnected 
from the miniature motor housing 2 and a base portion 24 connected to the 
miniature motor housing 2; 4 to a metallic member; 5 to an insulating 
brush base, made of a synthetic resin; 6 to a brush member; 7 to a recess 
formed on the metallic member; 8 to a terminal mount hole; 9 to a boss 
hole; 10 to a base recess; 10' to an inner side wall of the base recess 
10; 11 to a terminal mount; 11' to a terminal hole; 12 to a crimping boss; 
13 to a magnet retainer; 14 to a brush fixing member; 15 to a terminal; 16 
to a brush; 17 to a brush fixing pin; 18 to a permanent magnet; 19 to a 
rotor positioned in a motor chamber 25; 20 to a rotating shaft; and 21 to 
a bearing, respectively. 
A cover plate or cover member 1 shown in FIG. 1 is composed of the metallic 
member 4 and the insulating brush base 5. The metallic member 4 has a 
bearing 21 and a metallic member recess 7 formed by stamping forming a 
recess 7 on one side of the metallic cover plate member 4 and a protruding 
portion 27 on the opposite side, for example, a terminal mount hole 8 and 
a boss hole 9. The insulating brush base 5 is molded in a synthetic resin, 
and has a base recess 10 having a base recess side wall 10' for engagement 
with the metallic member recess 7, a terminal mount 11 having a terminal 
hole 11' into which a terminal is inserted, as will be described later, a 
crimping boss 12, a magnet retainer 13 for retaining a permanent magnet 
18, which will be described later, and a brush fixing member 14 for 
fixedly fitting a brush member 6. The cover plate of this invention is 
constructed by crimping the crimping boss 12 after the metallic member 4 
is disposed on the insulating brush base 5 so that the recess 7 of the 
metallic member 14 is engaged with the recess 10 of the insulating brush 
base 5, and the terminal mount 11 and the crimping boss 12 of the 
insulating brush base 5 are engaged with the terminal mount hole 8 and the 
boss hole 9 on the metallic member 4, respectively. On the cover plate 1, 
the terminal 15 of the brush member 6 is inserted into the terminal hole 
11' and the brush member 6 having the brush 16 is fixedly fitted by means 
of the brush fixing pin 17. 
As described above, the embodiment of this invention shown in FIG. 1 is 
completed by engaging the cover plate 1, to which the brush member 6 is 
fitted, with the open end of the motor housing 2 fitted with the permanent 
magnet 18 and the rotor 19 in the motor chamber 25, and crimping the 
recess 7 formed on the metallic member 4 comprising the cover plate 1 by 
means of the crimping pieces 3 formed on the motor housing 2. 
In the embodiment shown in FIG. 1, one end of the rotating shaft 20 of the 
rotor 19 is supported by the bearing (not shown) provided on the motor 
housing 2, and the other end thereof is supported by the bearing 21 
provided on the metallic member 4. 
As described in the foregoing, this invention, in which crimping is 
performed at recesses provided on the cover plate, makes it easy to 
position the cover plate when installing on the motor housing, enabling 
the cover plate to be firmly secured to the motor housing, thus preventing 
the cover plate from unwantedly rotating during motor rotation. The recess 
of the insulating brush base is isolated from the motor inside by the 
inner side wall of the base recess, making it possible to prevent dirt and 
dust from entering the motor inside.