Small brush motor

Details Small brush motor Small brush motor

2003-02-26

2004-11-23

Nguyen, Tran (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S198000, C310S220000

Reexamination Certificate

active

06822365

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a small brush motor of a four-magnetic-pole-six-salient pole structure provided with a varistor for suppressing overvoltage, and more particularly, to the winding state of an armature coil winding.
2. Description of the Related Art
As seen in Japanese Unexamined Patent Publication (Kokai) No. 11-69747, U.S. Pat. No. 6,153,960, and U.S. Pat. No. 6,285,109, in small brush motors of four-magnetic-pole-six-salient pole structures, motors are being increased in flatness, reduced in size, reduced in cost, and reduced in wiring defects by using three-electrode ring varistors usually used for two-magnetic-pole-three-salient pole structures as varistors for suppressing overvoltage (extinguishing spark arcs). For this, it is necessary to electrically connect the opposed risers in a point symmetric positional relationship about the center of rotation of the armature core among the six risers (terminal parts of commutator pieces). For the purpose of improving the productivity, etc., instead of using special printed circuit boards for connecting the risers or using the known commonly applied art of individual wiring using conductors, they are connected by using partial segments of the coil wrapped around the six salient poles so as to achieve a continuous pattern including the six risers.
That is, the armature
10
of this small brush motor, as shown in
FIGS. 7A and 7B
, is provided with a shaft
12
, an armature core
11
having six salient poles P
1
to P
6
in a radial array, a commutator
15
having six risers R
1
to R
6
positioned between the salient poles at one end face of the armature core
11
, a three-phase coil
17
comprised of a single wire continuously wound around the six risers R
1
to R
6
and the six salient poles P
1
to P
6
in the form of a continuous pattern, a ring varistor
19
for suppressing overvoltage having three electrodes (
19
a
,
19
a
,
19
a
) connected to every other one of the six risers R
1
to R
6
, that is, three risers (R
2
, R
4
, and R
6
), and a brush (not shown) for sliding contact with the commutator
15
. Further, this small motor is provided with a stator permanent magnet (not shown) having four magnetic poles.
Each phase coil of the three-phase coil
17
is obtained by winding the wire around a first riser (R
1
, R
3
, and R
5
) and a second riser (R
2
, R
4
, and R
6
) in a point symmetric positional relationship with respect to the center of rotation of the armature core
11
, then winding around the first salient pole (P
1
, P
3
, and P
5
) adjoining the second riser, then winding around a second salient pole (P
2
, P
4
, and P
6
) in a point symmetric positional relationship with the first salient pole (P
1
, P
3
, and P
5
) about the center of rotation of the armature core
11
. Each phase coil is attached using three risers and two salient poles.
Here, as shown by spreading open the peripheral end of the armature core in
FIG. 8A
, a first phase coil is comprised by knotting a winding start S to the riser R
1
, winding the wire in the forward rotation direction (arrow direction), knotting it with the riser R
4
opposed to the riser R
1
in a point symmetric positional relationship about the center of rotation of the armature core
11
, wrapping it around the adjoining salient pole P
1
in the forward rotation direction as the first coil part C
11
, then winding it in the reverse rotation direction and wrapping it around the salient pole P
2
opposed to the salient pole P
1
as the second coil part C
12
, then winding it in the reverse direction rotation and knotting it with the adjoining riser R
3
in the forward rotation direction of the salient pole P
1
. Next, the second coil is comprised by winding the wire in the reverse rotation direction from the riser R
3
, knotting it with the riser R
6
opposed to the riser R
3
, wrapping it around the adjoining salient pole P
3
in the forward rotation direction as the first coil part C
21
, then winding it in the reverse rotation direction and wrapping it around the salient pole P
4
opposed to the salient pole P
3
as the second coil part C
22
, then winding it in the reverse direction rotation and knotting it with the adjoining riser R
5
in the forward rotation direction of the salient pole P
3
. Next, the third phase coil is comprised by winding the wire in the forward rotation direction from the riser R
5
, knotting it with the riser R
2
opposed to the riser R
5
, wrapping it around the adjoining salient pole P
5
as the first coil part C
31
in the forward rotation direction, then winding it in the forward rotation direction and wrapping it around salient pole P
6
opposed to the salient pole P
5
as the second coil part C
32
, then knotting it with the adjoining riser R
4
in the forward rotation direction as the winding end E. Here, if expressing the forward rotation direction by the arrow mark →, the reverse direction rotation by the arrow mark
, and the length of the crossover wire between the salient poles, between the risers, and between a salient pole and a riser by rotational angle (radians) as a general measure and showing the winding order by simple symbols, the result becomes as follows:
Winding state shown in FIG.
8
A:
R
1
(
S
)(&pgr;)→
R
4
→(&pgr;/6)→
P
1
(&pgr;)
P
2
(&pgr;/3)
R
3
(&pgr;)
→(&pgr;/6)→
P
3
(&pgr;)
P
4
(&pgr;/3)
R
5
→(&pgr;)→
R
2
→(&pgr;/6)→
P
5
→(&pgr;)→
P
6
→(&pgr;/6)→
R
4
(
E
)
FIGS. 8B and 8C
show other continuous patterns.
Winding state shown in FIG.
8
B:
R
1
(
S
)→(&pgr;)→
R
4
→(&pgr;/6)→
P
1
→(&pgr;)→
P
2
→(&pgr;/6)→
R
6
→(&pgr;)→
R
3
→(7&pgr;/6)→
P
3
→(&pgr;)→
P
4
→(&pgr;/6)→
R
2
→(&pgr;)→
R
5
→(7&pgr;/6)→
P
5
→(&pgr;)→
P
6
→
R
4
(
E
)
Winding state shown in FIG.
8
C:
R
1
(
S
)→(7&pgr;/6)→
P
1
(&pgr;/6)
R
4
→(&pgr;/6)→
P
1
(&pgr;)
P
2
(5&pgr;/6)
R
3
→(&pgr;/6)→
P
4
(7&pgr;/6)
R
6
→(&pgr;/6)→
P
3
(&pgr;)
P
4
→(5&pgr;/6)
R
5
(
E
)
Summarizing the problems to be solved by the present invention, even with the small brush motor of the above four-magnetic-pole-six-salient-pole structure, greater flatness, smaller size, and higher torque are being demanded. As a motor is made flatter and smaller, however, the coil area per salient pole also becomes smaller and increasing the torque becomes difficult. In general, there is a tradeoff between greater flatness and smaller size and higher torque. In general, along with greater flatness and smaller size, the coil has to be made finer, but with a single coil, if the number of turns is increased, the wire length will become longer, so the resistance loss (copper loss) will become greater. As a means for easing this to some extent, if winding a coil comprised of N (natural number) number of ultrafine wires arranged in parallel by a continuous pattern, at the coil part at each salient pole, as compared with winding a single ultrafine wire as the coil in a continuous pattern, the wires become denser and the coil area can be increased to a certain extent and also the copper loss can be suppressed using the surface film effect due to the relative increase in the surface area of the wires. Therefore, even with greater flatness and smaller size, the torque can be increased to a certain extent.
In general, however, when using ultrafine wire as the coil, the tensile strength becomes considerably weaker and disconnection easily occurs, so it is necessary to shorten the length of crossover wires between salient poles, between risers, and between risers and salient poles as much as possible. Further, when fixing wires conductively by soldering, etc., to the knotting parts of the risers R
1
to R
6
, the heat of melting is conducted from the risers to the crossover wires, so it is necessary to eliminate cross points between crossover wires between different phase coils and prevent short-circuits between d

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