Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2002-03-01
2003-12-09
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S239000, C310S050000, C310S071000, C310S241000, C310S049540, C310S089000
Reexamination Certificate
active
06661148
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cooling air passage in a motor-driven tool having a cooling fan, such an impact driver or the like.
2. Description of the Related Art
A conventional motor-driven tool will be described referring to
FIGS. 6
to
9
. The conventional motor-driven tool as shown in
FIGS. 6 and 7
has a substantially T-shape. In a body part composed of a housing
5
which is divided in two and constitutes a main body of the motor-driven tool (hereinafter referred to as “a housing”), there are arranged a motor which is a power source, a reduction gear mechanism, and so on, and in a handle part hanging down from the body part, there are arranged a trigger switch for supplying a power to the motor, and so on. There are also provided, in the above mentioned body part, a carbon brush block
8
for holding a carbon brush
17
which supplies a power to an armature
1
of the motor, and so on. These carbon brush block
8
and so on are clamped by the housing
5
to be held at a determined position in the housing
5
. There are further formed a rib
5
a
in the housing
5
in order to receive and position a stator
3
. Because the rib
5
a
supports the stator
3
at its left side face, an air entering from a suction port
21
provided in the housing
5
is blocked by the rib
5
a
and the stator
3
, and flows along an outer peripheral wall of the stator
3
to the right in
FIG. 7
, as shown by an arrow B′ in FIG.
7
. Then, the air flows between the stator
3
and the armature
1
to the left in
FIG. 7
, and thereafter, will be discharged from a discharge port
7
to an exterior of the housing
5
. The carbon brush block
8
consists of a carbon tube
9
, a carbon cap
18
, a lead wire
19
and so on. This carbon brush block
8
is arranged in such a manner that the carbon brush
17
can be attached and detached from the exterior of the housing.
At a side of the armature
1
opposite to its output side, there is provided a cooling fan
2
. When this cooling fan is rotated, an air around the cooling fan
2
is discharged from the discharge port
7
provided in the housing
5
, and accordingly, a negative pressure is created in the housing
5
to form a difference in pressure between an inside and an outside of the housing. As the results, airs flow into the housing through suction ports
20
and
21
provided in the housing
5
. The armature
1
, the carbon brush
17
, the carbon tube
9
and so on are cooled by these flows of the air (the arrows B, B′ in FIG.
7
). The air flowing into the housing
5
from the suction port
20
is mainly used for cooling a commutator
11
, the carbon brush
17
, the carbon tube
9
and so on, while the air flowing into the housing
5
from the suction port
21
is mainly used for cooling the armature
1
which is a heat source.
The conventional motor-driven tool as shown in
FIGS. 8 and 9
has a substantially T-shape. In a body part composed of a housing
5
constituting the main body of the motor-driven tool, there are arranged a motor which is a power source, a reduction gear mechanism, and so on, and in a handle part hanging down from the body part, there are arranged a trigger switch for supplying a power to the motor, and so on. There are also provided in the body part a carbon brush block
8
for holding a carbon brush
17
which supplies a power to an armature
1
of the motor, and so on. These carbon brush block
8
and so on are provided in a casing
22
which contains the armature
1
and a stator
3
.
At a side of the armature
1
opposite to its output side, there is provided a cooling fan
2
. When this cooling fan
2
is rotated, an air around the cooling fan
2
is discharged from a discharge port
7
provided in the casing
22
to an exterior of the casing
22
, and accordingly, a negative pressure is created in the casing
22
to form a difference in pressure between an inside and an outside of the casing
22
. As the results, airs flow into the casing
22
through suction ports
6
and
6
′ provided in the casing
22
. The armature
1
, the carbon brush
17
, the carbon tube
9
and so on are cooled by these flows of the air (arrows C, C′ in FIG.
9
).
In the cooling structure of the motor-driven tool as shown in
FIGS. 6 and 7
, there has been a problem that because the air for cooling the armature (the arrow B′ in
FIG. 7
) flows along an outer periphery of the stator, an air passage (distance) from the suction port to the armature becomes long, resulting in a serious loss of pressure and decrease of cooling efficiency, and consequently, the armature will be burnt to be broken at an earlier stage.
On the other hand, in the cooling structure of the motor-driven tool as shown in
FIGS. 8 and 9
, because the air for cooling the armature is not an air passage flowing along the outer periphery of the stator, the armature can be cooled by the air flow as shown by the arrow C in FIG.
9
. However, there has been a problem that since the air entering into the casing from the suction port at the carbon brush side (the arrow C′ in
FIG. 9
) flows into a large space which is formed between the casing and the carbon brush and so on, velocity of the flow will be lowered, and strong cooling air cannot be applied to the commutator, the carbon brush and the carbon tube. As the results, heat generation of the carbon brush and the carbon tube cannot be prevented, resulting in fusion of the carbon cap and so on.
SUMMARY OF THE INVENTION
It is an object of the invention to solve the above described problems and attain a long life of a motor-driven tool by reliably cooling a surrounding area of a motor, and at the same time, by decreasing a pressure loss.
The above described object will be attained by providing a motor-driven tool comprising a motor consisting of an armature and a stator, a cooling fan provided on a rotary shaft of the motor, a carbon brush part adapted to be cooled by the cooling fan, and a housing for containing the carbon brush part and the motor, the housing being provided with a suction port and a discharge port, characterized in that the carbon brush part is arranged including a cylindrical side wall between the suction port and a commutator of the motor, the cylindrical side wall located close to an outer periphery of the commutator being provided with a tapered portion which grows wider toward the commutator and grows narrower toward a coil end of the armature, and that between the carbon brush part and the coil end, there is provided a heat radiating plate made of metal and adapted to be engaged with the carbon brush part.
REFERENCES:
patent: 3813567 (1974-05-01), Schmuck
patent: 4562368 (1985-12-01), Weldon
patent: 5949173 (1999-09-01), Wille
patent: 4-43365 (1992-04-01), None
patent: 6-84776 (1994-12-01), None
patent: 10-136611 (1998-05-01), None
patent: 10136611 (1998-05-01), None
Nemoto Toshiyuki
Ohtsu Shinki
Oomori Katsuhiro
Saito Takuma
Watanabe Masanori
Hitachi Koki Co,. Ltd.
McGinn & Gibb PLLC
Mohandesi Iraj A.
Ramirez Nestor
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