Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-11-12
2002-12-31
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S232000
Reexamination Certificate
active
06501207
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an a.c. generator mounted on a vehicle, in particular, the present invention relates to portions of the generator for leading out both ends of a rotor coil.
2. Discussion of Background
FIGS. 5 through 8
show the structure and the problems of a conventional vehicular a.c. generator.
FIG. 5
shows a cross-sectional view of the a.c. generator.
FIG. 6
shows a perspective view of a rotor with a portion of a cooling fan cut away.
FIG. 7
shows a detail view of a portion of the generator, where an end of a rotor coil is led out.
FIG. 8
shows a schematic view to explain how vibration is applied to a rotor core. Referring to
FIG. 5
, reference numeral
1
designates a stator, which comprises a front bracket
2
, a rear bracket
3
and a stator core
5
with a stator coil
4
. Reference numeral
6
designates the rotor, which comprises a pair of rotor cores
7
and
8
, the rotor coil
9
sandwiched between the rotor cores
7
and
8
, and a rotary shaft
10
. The rotary shaft
10
has a portion thereof near the front bracket
2
provided with a pulley
11
and a portion thereof near the rear bracket
3
provided with slip rings
12
for supplying an exciting current to the rotor coil
9
. The rotor core
7
has a front fan
13
provided thereon, and the rotor core
8
has a rear fan
14
provided thereon.
On the rear bracket
3
are provided a brush holder
16
with brushes
15
in slidable contact with the slip rings
12
, a rectifier
17
for rectifying an a.c. output from the stator coil
4
, and a voltage regulator
18
for controlling the output voltage from the stator coil. In the rotor
6
, the rotor cores
7
and
8
alternately provide magnetic poles
19
and
20
as shown in FIG.
6
. The rotor coil
9
is wound on a bobbin
21
and sandwiched between the rotor cores
7
and
8
as shown in FIG.
5
. The rotor coil
9
has lead wires
9
a
at its wind-start portion and its wind-completion portion. The respective lead wires are held by fixing portions
21
a
formed on the bobbin
21
, extend into respective grooves
8
a
formed in the rotor core
8
so as to be electrically protected by insulating sleeves, are fixed at respective hooks
12
a
formed on the respective slip rings
12
, and are connected to connecting terminals
12
b
by spot-welding or a similar technique.
Wiring of the lead wires
9
a
is carried out on an automatic machine. The automatic machine requires that the grooves
8
a
formed in the rotor core
8
be directed in a direction deviated from a radial direction from each of the fixing portions
21
a
toward the center of the rotary shaft
10
. By this arrangement, the lead wires
9
a
, which are provided in the grooves
8
a
from the fixing portions
21
a
to the hooks
12
a
, are subjected to a centrifugal force in a bending direction. The grooves
8
a
have a resin filled on bottoms thereof to bond the lead wires
9
a
thereto so as to cope with the centrifugal force. As shown in
FIG. 7
, the lead wires extend in space and apart from the bottoms of the grooves
8
a
to be connected to the connecting terminals
12
b
at locations where the lead wires are fixed to the hooks
12
a
. In
FIG. 6
is shown only one of both lead wires at the wind-start portion and at the wind-completion portion.
In the a.c. generator thus constructed, the stator coil
4
generates a.c. power when an exciting current is supplied to the rotor coil
9
through the brushes
15
and the slip rings
12
with the rotor
6
driven by an internal combustion engine. The rectifier
17
converts the a.c. power into d.c. power before outputting the power from the generator. The voltage regulator
18
regulates the exciting current to control the output voltage from the generator. Since the stator coil
4
, the rectifier
17
and the voltage regulator
18
produce heat, the front fan
13
and the rear fan
14
provided on the rotor cores
7
and
8
introduce external air to constantly cool these devices in operation.
The conventional a.c. generator has a great speed increasing ratio with respect to the driving internal combustion engine since the generator can provide sufficient output even in a low revolution range. The conventional generator has recently reached a maximum at 18,000 RPM. Under the circumstances, the lead wires
9
a
, which are provided in a direction deviated from a radial direction starting at the center of revolution, are subjected to a great centrifugal force. Additionally, significant angular accelerations, that are caused by variations in the revolution of the internal combustion engine, are applied to the rotor
6
. As a result, the lead wires
9
a
are subjected to a great stress. In addition, the rotor core
8
is subjected to vibrations caused by the electromagnetic attraction between the magnetic poles
20
of the rotor core
8
and the stator core
5
as shown in FIG.
8
. The vibrations create a problem in that the resin, which has been filled in a groove
8
a
to bond the relevant lead wire
9
a
to the bottom thereof is exfoliated from the bottom of the groove
8
a
at an outer side of the rotor core
8
.
In the case of a vehicular a.c. generator rated at 100 A as output for instance, the caloric value of the stator coil
4
is about 500 W at the maximum, and the caloric value of the rectifier
17
is about 120 W at the maximum. Although the front fan
13
supplies air to the stator coil
4
to cool the stator coil and the rear fan
14
also supplies air to the stator coil
4
, the temperatures of the stator coil
4
and the rectifier
17
are raised to about 200° C. when the engine room is at a temperature of 100° C. The cooling air supplied by the rear fan
14
cools the rectifier
17
and the voltage regulator
18
as indicated in an arrow A in
FIG. 5
, and is heated by cooling the rectifier
17
and the voltage regulator
18
. The heated air passes the outer side of the rotor core
8
. Additionally, the rotor coil
9
produces heat at about 60 W. Under these circumstances, the lead wires
9
a
and the bonding resin in the grooves
8
a
in the outer side of the rotor core
8
are exposed to a high temperature, which can reach temperatures of up to 150° C. in some cases.
As explained, the lead wires
9
a
are subjected to high temperatures and the stresses caused by the vibrations and the centrifugal forces during operation. Such operating conditions are made even more severe because of demands to obtain high output from the generator and to operate the generator faster. This has created a problem in that the resin, which has been provided to bond the lead wires
9
a
to the bottoms of the grooves
8
a
, is deteriorated to cause separation of the resin from the bottoms of the grooves
8
a
, causing the lead wires to be cut off. In addition, the resin that has separated is flown by the centrifugal force in the generator. The flown resin could come between the stator core
5
and the rotor cores
7
and
8
, damage the insulation of the stator coil
4
or another device, or damage a brush
15
, which is an additional problem.
In order to cope with these problems, there has been proposed a technique as disclosed in JP-Y-644296. In this technique, a fan, which is provided on a rotor core, has an inner circumferential portion engaged with an outer circumferential portion of slip rings, lead wires of the rotor coil are surrounded by a slip ring and a barrier provided on the fan at a location to connect the lead wires to the slip rings, and an insulated material is filled in the space defined by the slip ring and the barrier for fixing of the lead wires. By this arrangement, even if the insulated material separates from the rotor core because of thermal deterioration or another factor, the centrifugal force can be received by the barrier provided on the fan to reduce the stress applied to the lead wires. However, this arrangement can not provide complete measures to avoid the disconnection between the resin and the rotor core since a thermal stress is applied to a conn
Asao Yoshihito
Kashihara Toshiaki
Oohashi Atsushi
Mitsubishi Denki & Kabushiki Kaisha
Tamai Karl
LandOfFree
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