Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-09-04
2004-09-07
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S239000, C310S248000, C310S249000, C310S251000
Reexamination Certificate
active
06787962
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a starter with an overheat-protection device including a brush device having a thermostat adapted to interrupt energization of a starting motor when a brush in the starting motor continuously energized exceeds a predetermined temperature due to self-heating of the brush, whereby the energization of the stating motor with a power supply is interrupted.
2. Description of the Related Art
FIG. 14
is a cross-sectional view of the essential part of a conventional starter.
FIG. 15
is a perspective view of a heat-reception member shown in FIG.
14
.
FIG. 16
is an electric circuit diagram of the starter of FIG.
14
.
In
FIG. 14
, a starting motor
1
comprises a shaft
2
rotatably supported by a bearing
5
, an armature
3
fixed to the shaft
2
, plural commutator pieces
4
arranged adjacently to the armature
3
and in the periphery of the shaft
2
, brushes
6
having a substantially parallelepiped rectangular shape, in contact with the commutator pieces
4
at four positions thereof, and brush holders
7
slidably supporting the brushes
6
.
The starting motor
1
is supported in a bracket
8
. Bases
9
are fixed to the bracket
8
. Each brush holder
7
is fixed to the base
9
via an insulation plate
10
, which is an electric insulation member, and a heat-reception member
11
by means of rivets.
The heat-reception member
11
, formed by working a brass flat sheet, contains a plane portion
11
a
having holes
11
c
for fixing the rivets, sandwiched between the brush holder
7
and the insulation sheet
10
, and a thermostat-attachment portion
11
b
bent perpendicularly, immediately from the plane portion
11
a
, and extending therefrom.
A thermostat
12
is fixed to the thermostat-attachment portion
11
b
via an insulation tube
13
by means of an adhesion tape
14
. The insulation tube
13
covers the thermostat
12
so that the thermostat
12
is prevented from directly contacting the heat-reception member
11
. Thus, the electric insulation of the thermostat
12
from the brush
6
and the bracket
8
is secured.
The thermostat
12
comprises a case
15
and a bimetal
18
housed in the case
15
. The bimetal
18
, when the temperature exceeds a predetermined value, is bent-distorted to interrupt the energization.
In
FIG. 16
, the starter is provided with the starting motor
1
, a battery
30
as a power supply, a start-switch
31
provided as a key switch, an auxiliary switch
32
, the thermostat
12
connected in series with the auxiliary switch
32
, and a magnet switch
36
.
The auxiliary switch
32
comprises a pair of fixed contacts
33
, a movable contact
34
, and an excitation coil
35
.
The magnet switch
36
comprises a pair of main fixed contacts
37
, a main movable contact
38
interlocked with a plunger (not shown) to contact the main fixed contacts
37
and turn on-off a main current to the starting motor
1
, an attraction coil
39
which becomes a resistor for a fine current flowing into the starting motor
1
till a pinion gear becomes engaged (for the time till the main movable contact
38
contacts the main fixed contact
37
) and also having a function of generating an attraction force which causes the pinion gear (not shown) to be engaged with the ring gear of an internal combustion engine, and a holding coil
40
for holding the contact of the main movable contact
38
with a pair of the main fixed contacts
37
.
From the thermostat
12
, a lead wire
17
connected to an excitation coil
35
, and also, a lead wire
16
connected to a connector
21
are led out, respectively.
Hereinafter, operation of the starter configured as described above will be described. First, when a driver turns on the start switch
31
by operation of the key switch, current flows from the battery
30
into the thermostat
12
and the excitation coil
35
, so that the excitation coil
35
is excited. As a result, the movable contact
34
is moved, so that the fixed contacts
33
are electrically connected to each other, and the auxiliary switch
32
becomes on. At the same time, fine current flows from the battery
30
into the starting motor
1
via the attraction coil
39
, so that the starting motor
1
is driven at a low rotation speed, and current also flows into the holding coil
40
.
When the current flows into the attraction coil
39
, an attraction force is generated in the attraction coil
39
. With the attraction force, the plunger is moved, and a shift lever engaged and stopped at the end of the plunger is rotated to press the pinion gear toward the ring gear side of the internal combustion engine, so that the pinion gear is engaged with the ring gear. Also, the main movable contact
38
is interlocked with the plunger. The main movable contact
38
is interlocked with the plunger. When the pinion gear becomes normally engaged with the ring gear, the main movable contact
38
comes into contact with the main fixed contact
37
, and main current from the battery
30
flows directly into the starting motor
1
, so that the starting motor
1
is rotated, and the internal combustion engine starts.
After the internal combustion engine starts, the start switch
31
is turned off by driver's operation of the key switch, so that the energization of the auxiliary switch
32
, the magnet switch
36
, and the starting motor
1
by means of the battery
30
is interrupted. As a result, the attraction force at the attraction coil
39
becomes null, the engagement of the pinion gear with the ring gear is released, and rotation of the starting motor
1
stops.
In the event that the start switch
31
is not turned off, caused by a defect in return of the key switch or the like, so that current continues to flow from the battery
30
into the starting motor after the internal combustion engine starts, for example, there is the danger that thermal damages such as dielectric breakdown between the armature
1
and the commutator pieces
4
of the starting motor
1
, or the like may occur.
To prevent such excessively continuous energization of the starting motor
1
, the thermostat
12
is contained in the starter.
If current continues to flow in the starting motor
1
after the internal combustion engine starts, heat (hereinafter, referred to as brush heat) is generated in each of the brushes
6
so that the brush
6
have a high temperature. The heat is conducted to the thermostat
12
via the heat reception member
11
so that the temperature of the thermostat
12
rises. When the thermostat
12
reaches a predetermined temperature or higher, the bimetal
18
is bent-distorted to interrupt the energization, and the excitation of the excitation coil
35
becomes null. The movable contact
34
is separated from the fixed contact
33
, and the auxiliary switch
32
becomes off. As a result energization of the attraction coil
39
, the starting motor
1
, and the holding coil
40
becomes null. Thus, thermal damages such as dielectric breakdown between the armature
3
and the commutation pieces
4
of the starting motor
1
can be prevented.
The insulation plate
10
is provided between the heat reception member
11
and the base
9
. Thus, heat is suppressed from escaping from the base
9
side. Thus, the brush heat is ready to be conducted to the thermostat
12
.
In the starter having the above-described configuration, the brush heat is conducted to the thermostat
12
via the heat reception member
11
. However, since the heat reception member
11
has a heat resistance, and there is a distance between the brush
6
and the thermostat
12
, the thermostat
12
can not quickly respond to a rise in temperature of the brush heat by any means. Accordingly, there arises the problem that current continues to flow in the starting motor
1
though the brush
6
exceeds a predetermined temperature, and thermal damages such as dielectric breakdown between the armature
1
and the commutator pieces of the starting motor
1
become severer.
As a countermeasure against the above problem, the
Ikeda Hirohide
Kusumoto Keiichi
Nishii Kazuhide
Seta Akio
Yagi Katsunori
Elkassabgi Heba
Mitsubishi Denki & Kabushiki Kaisha
Mullins Burton S.
Sughrue & Mion, PLLC
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