Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-12-18
2003-09-23
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S254100, C310S207000, C310S198000, C310S184000, C310S179000, C310S180000, C310S071000, C310S06800R
Reexamination Certificate
active
06624544
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stator for an alternator driven by an internal combustion engine, for example, and in particular, relates to the construction of neutral-point lead terminals in a stator winding of a three-phase alternator.
2. Description of the Related Art
FIG. 9
is a cross section showing a conventional alternator.
In
FIG. 9
, the alternator is provided with: a case
3
constructed from an aluminum front bracket
1
and an aluminum rear bracket
2
; a shaft
6
rotatably mounted inside the case
3
, a pulley
4
being fastened to a first end of the shaft
6
; a Lundell-type rotor
7
fastened to the shaft
6
; fans
5
fastened to both axial ends of the rotor
7
; a stator
8
fastened to an inner wall of the case
3
so as to cover an outer circumferential side of the rotor
7
; slip rings
9
fastened to a second end of the shaft
6
for supplying electric current to the rotor
7
; a pair of brushes
10
which slide in contact with the slip rings
9
; a brush holder
11
for holding the brushes
10
; a rectifier
12
which is electrically connected to the stator
8
to convert alternating current generated in a stator winding
16
of the stator
8
into direct current; a heat sink
17
fitted onto the brush holder
11
; and a regulator
18
mounted on the heat sink
17
for adjusting the output voltage generated in the stator
8
.
The rotor
7
is composed of a rotor winding
13
for generating magnetic flux on passage of electric current, and a pair of pole cores
20
and
21
disposed so as to cover the rotor winding
13
, magnetic poles being formed in the pole cores
20
and
21
by magnetic flux generated in the rotor winding
13
. The pair of pole cores
20
and
21
are made of iron, each has a number of claw-shaped magnetic poles
22
and
23
disposed on an outer circumferential perimeter at even pitch in a circumferential direction so as to project axially, and the pole cores
20
and
21
are fastened to the shaft
6
facing each other such that the claw-shaped magnetic poles
22
and
23
intermesh.
The stator
8
is provided with a stator core
15
, and a stator coil
16
which generates alternating current due to changes in magnetic flux produced by the rotor winding
13
accompanying the rotation of rotor
7
wound to the stator core
15
.
In the automotive alternator constructed in this manner, electric current is supplied from a battery (not shown) through the brushes
10
and the slip rings
9
to the rotor winding
13
, generating magnetic flux. The claw-shaped magnetic poles
22
of the pole core
20
are magnetized with north-seeking (N) poles by this magnetic flux, and the claw-shaped magnetic poles
23
of the pole core
21
are magnetized with south-seeking (S) poles. At the same time, rotational torque from the engine is transmitted through the belt and the pulley
4
to the shaft
6
, rotating the rotor
7
. Thus, a rotating magnetic field is applied to the stator winding
16
, generating electromotive force in the stator coil
16
. This alternating electromotive force passes through the rectifier
12
and is converted into direct current, the output thereof being adjusted by the regulator
18
, and the battery being recharged.
The stator winding
16
of the stator
8
is generally a three-phase star connection, and the construction of the neutral-point connections therein is as shown in Japanese Patent Publication No. HEI 7-32555, for example.
In other words, as shown in
FIG. 10
, three winding phase portions are formed by winding strands of wire
24
into the stator core
15
for a required number of turns, the strands of wire
24
being composed of conducting wires having a circular cross section, and neutral-point terminals
25
of the three winding phase portions are led out from a coil end group, the three led-out neutral-point terminals
25
being brought together in one place and connected together by twisting. Then, as shown in
FIG. 11
, the three twisted neutral-point terminals
25
are fastened and integrated by soldering to form a neutral-point joint portion
27
which is a joint portion joining the three neutral-point terminals
25
. In addition, although not shown, a neutral-point lead portion is disposed on the neutral-point joint portion
27
.
Then, the neutral-point lead portion extending outwards from the neutral-point joint portion
27
extends outwards from the stator core
15
together with output terminals (output wires)
29
of each of the winding phase portions, and the neutral-point lead portion and the output terminals
29
are fastened by means of crimping to a terminal on a circuit board
12
a
in the rectifier
12
and are electrically connected by soldering, respectively. Thus, an alternator is provided in which output can be increased when the alternator is rotating at high speed by adding neutral-point voltage to the direct current output.
The neutral-point joint portion
27
is fastened and integrated by soldering the three neutral-point terminals
25
, but in cases where the stator winding is constituted by two sets of the three winding phase portions, the neutral-point joint portion may be constructed by bringing six neutral-point terminals together in one place, connecting them by twisting them together, and fastening and integrating them by soldering.
It is desirable that the neutral-point lead portion and the output wires
29
extend outwards from the stator core
15
parallel to the axial direction to facilitate connection to the circuit board
12
a.
Furthermore, because the neutral-point terminals
25
are led around, brought together in one place and soldered, there are cases when excessive leading around of the neutral-point terminals
25
occurs due to the relative positions of the slots in which the neutral-point terminals
25
are housed. Because the long lead-around of the neutral-point terminals
25
gives rise to problems such as bringing about an increase in the amount of conducting wire, which is a heat-generating body, in other words, an increase in the amount of heat generated and an increase in electrical resistance, reducing power-generating efficiency, or giving rise to breakage of the winding and interference with other parts due to vibration when the alternator is mounted to a vehicle, it is desirable to make the lead-around of the neutral-point terminals
25
as short as possible.
In order to suppress vibration of the neutral-point joint portions
27
and the neutral-point lead portions in the presence of vibration when the alternator is mounted to the vehicle, measures have been taken to secure the lead-around portions of the neutral-point terminals
25
by binding them to the coil ends using tie-shaped bodies passing through coil end apex portions, or applying varnish to fix them to the coil ends. However, when the lead-around portions are secured to the coil ends using tie-shaped bodies, the tie-shaped bodies must be passed between the narrow spaces between the strands of wire on the coil end apex portions, decreasing work efficiency, and when the lead-around portions are secured to the coil ends by applying varnish, it is difficult to obtain a sufficient degree of securing strength with a low-viscosity varnish because the lead-around portions and the coil ends are separated by a predetermined spacing, and improvements have been called for.
In the neutral-point joint portions
27
in a stator winding
16
constructed in this manner, because a number of neutral-point terminals
25
are gathered together in one place and twisted together into a bundle then fastened and integrated by soldering, the solder
26
cannot enter between the twisted neutral-point terminals
25
, and a cavity A is formed in a central portion, as shown in
FIG. 12
, and one problem has been that sufficient joint strength cannot be achieved, making it difficult to ensure reliability.
Because a number of neutral-point terminals
25
are soldered together, another problem has been that a high capacity jig is needed and it is necessary to heat
Adachi Katsumi
Asao Yoshihito
Higashino Kyoko
Cuevas Pedro J.
Mitsubishi Denki & Kabushiki Kaisha
Ramirez Nestor
Sughrue & Mion, PLLC
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