Vehicle-onboard AC generator

Details Vehicle-onboard AC generator Vehicle-onboard AC generator

2001-02-16

2003-12-16

Le, Dang (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S06800R, C310S06800R

Reexamination Certificate

active

06664677

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an alternating current or AC generator destined for use in an automobile or motor vehicle (hereinafter, this type generator will also be referred to as the vehicle-onboard AC generator). More particularly, the present invention is concerned with an improvement concerning an arrangement for interconnection of stator windings of the vehicle-onboard AC generator.
2. Description of Related Art
Before entering into description of the vehicle-onboard AC generator according to the present invention, technical background thereof will be reviewed in some detail for having better understanding of the concept underlying the invention.
FIG. 15
is a sectional view showing a conventional AC generator which has heretofore been known. Referring to the figure, the illustrated AC generator is comprised of a housing or case
3
made of aluminum, which case includes a front bracket
1
and a rear bracket
2
. A shaft
6
is rotatably mounted on the brackets
1
and
2
by means of roll bearings within the case
3
, and a pulley
4
is mounted at one end thereof. A landaulet type rotor
7
is fixedly mounted on the shaft
6
for corotation therewith. A pair of fans
5
are fixedly secured to both surfaces, respectively, of the rotor
7
for the purpose of cooling. A stator
8
is stationarily mounted on an inner wall of the case
3
. A slip ring
9
is fixedly mounted on the shaft
6
at the other end portion thereof for supplying an electric current to the rotor
7
. A pair of brushes
10
are disposed in slidable contact with the slip ring
9
. A brush holder
11
is so disposed as to accommodate therein and support the brushes
10
. A rectifier device
12
is electrically connected to the windings of the stator
8
for rectifying an alternating current induced in the stator windings into a direct current. A heat sink
17
is physically coupled to the brush holder
11
. Further, a regulator
18
is fixedly secured onto the heat sink
17
for adjusting or regulating the magnitude of an AC voltage induced in the stator winding assembly.
The armature rotor
7
is composed of a rotor coil
13
through which a direct current supplied from a battery (not shown) is caused to flow for generating magnetic fluxes. A pole core is so disposed as to encase therein the rotor coil
13
and has magnetic poles formed by the magnetic fluxes. More specifically, the pole core is constituted by a first pole core member
20
and a second pole core member
21
which are complementarily meshed together for thereby constituting the pole core.
On the other hand, the stator
8
is constituted by a stator core
15
and stator windings (also referred to generically as the stator winding assembly)
16
each of which is formed by winding an electric conductor on the stator core
15
and in which an alternating current is induced under the effect of changing of the magnetic fluxes emanated from the rotor coil
13
. Incidentally, arrows shown in
FIG. 15
represent flows of cooling air generated by the fans
5
.
In the vehicle-onboard AC generator implemented in the structure described above, a DC current is supplied to the rotor coil
13
from a battery (not shown) by way of the brushes
10
and the slip ring
9
, whereby magnetic fluxes are generated by the rotor coil
13
. As a result of this, the first pole core member
20
is magnetized in N-polarity while the second pole core member
21
is magnetized in S-polarity. On the other hand, the pulley
4
of the AC generator is driven by an engine such as an internal combustion engine of the motor vehicle on which the AC generator is installed, whereby the shaft
6
and hence the rotor
7
are caused to rotate in unison. Consequently, the stator windings are exposed to the rotating magnetic fields, which results in generation of an alternating current in the stator winding assembly
16
under the effect of electromagnetic induction. The alternating current as generated is supplied to the rectifier device
12
to be thereby rectified into a direct current, the magnitude of which can be adjusted by the regulator
18
. The direct current outputted from the rectifier device
12
is ultimately charged in the battery.
FIG. 16
is a perspective view showing a structure of the stator of the conventional AC generator, and
FIG. 17
is an equivalent circuit diagram thereof. Referring to
FIG. 16
, the stator windings
16
are each formed by winding a round wire conductor and accommodated or housed stationarily within slots formed in the stator core
15
. As can be seen in
FIG. 16
, the stator winding assembly
16
is comprised of lodged portions
161
housed within the slots and coil end portions
162
projecting, respectively, beyond both ends of the stator core
15
.
Referring to
FIG. 17
, the stator windings
16
are interconnected in a star connection in order to realize a three-phase AC generator circuit. End portions of the three conductors led out from the individual windings of the stator winding assembly are connected together to form a neutral point in the form of a neutral point junction
22
. Further, interconnecting portions
23
are provided for interconnecting the conductors brought out from the stator windings and terminals of the three-phase rectifier device
12
. Further, for the purpose of taking out the output power from the neutral point junction
22
, an output power conductor
24
is electrically connected to the neutral point junction
22
, although it depends on the design conditions. In that case, the neutral point junction
22
is realized by connecting together the end portions of four electric conductors in total.
In this conjunction, it is further noted that in recent years, there is a tendency that a thick conductor of a large diameter is employed for forming the stator winding assembly in an attempt for implementing the three-phase AC generator having a high output capacity. To this end, a so-called bifilar-winding or W-winding in which a single winding conductor is divided into two coextensive conductors is increasingly adopted. In the case of the stator composed of the bifilar type windings, one neutral point junction
22
is provided at one location on one side, while in the case of the W-winding type, two neutral point junctions
22
have to be provided at two locations on both sides, respectively, as can be seen in FIG.
17
. In any case, the output power conductors
24
have to be brought out from the neutral point junction(s)
22
.
The output power conductor
24
mentioned above is made of tough pitch copper, and each joint forming the interconnecting portion is realized by soldering. After the soldering, the conductor portions forming the neutral point junction
22
are encased within an insulation tube
25
. In succession, the encased conductor portion is laid or bent along the coil end portion to be subsequently fixed by applying a varnish or the like with a view to ensuring a vibration withstanding capability. Of course, the joint described above may be realized by using heterogeneous metal, as disclosed in Japanese Patent Application Laid-Open Publication No. 115743/1995 (JP-A-7-115743).
In the conventional vehicle-onboard AC generator of the structure described above, when interconnection of the conductors brought out from the individual windings has to be made internally of the stator
8
, the output power conductor
24
extending from the round wire conductors have to be wired along the circumference defined by the coil end portions
162
, involving difficulty in automatization of the wiring by machine.
Further, since the conductor portions forming the neutral point junction
22
are encased within the insulation tube
25
and laid on and along the coil end portions
162
to be subsequently fixed by a varnish, a heat radiation property of these conductor portions is poor when compared with the conductors of other winding portions, incurring high temperature rise. Consequently, thermal deterioration of these conductor portions as well as the

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