Alternator

Details Alternator Alternator

2000-08-23

2002-05-28

Mullins, Burton S (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S179000, C310S184000, C310S201000

Reexamination Certificate

active

06396185

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine, for example, and in particular, relates to a stator construction for an automotive alternator mounted to an automotive vehicle such as a passenger car or a truck.
2. Description of the Related Art
In recent years, compact high output and improvements in quality have been increasingly required of alternators. In order to achieve compact high output, it is important to design constructions which distribute magnetic loading and electrical loading in the most appropriate manner, and with the highest possible density within a limited volume.
For example, as engine compartments become progressively smaller, mounting space for automotive alternators is becoming less and less free, but at the same time, improvements in alternator output are required because of increases in automotive vehicle loads. Furthermore, there is increased need for noise reduction both inside and outside automotive vehicles, and although engine noise has been reduced, noise from automotive alternators, which run constantly to generate electricity in order to supply the electrical load for the vehicle, has remained a problem. Fan noise and magnetic noise in particular have been problems in automotive alternators which operate in a wide range of rotational frequencies from low to high speed.
Because automotive alternators are constantly generating electricity, they generate a lot of heat due to the joule heat of the output electric current and are subjected to a severe heat environment, requiring extremely high heat resistance.
Furthermore, within the engine compartment, an automotive alternator is often mounted directly onto an engine, where it is exposed to liquids such as engine oil and antifreeze, in addition to rain water, salt water, mud, etc., conditions where the corrosive environment is extremely severe. There are problems due to corrosion which lead to interruptions in power generation, etc., but most causes of interruption to power generation are the result of damage to insulation on a winding which occurs during the process of manufacturing a stator, or due to electrical short-circuiting in structurally exposed portions of the winding.
For compact high output by alternators, in particular, it is necessary to increase the space factor of electrical conductors housed within magnetic circuits of the stator, and to line up and increase the density of bridge portions of the stator winding (bridge portions outside a stator core are called coil ends), and in addition to this, various improvements have been proposed in order to answer the requirements for low noise, heat-resistance, corrosion resistance, etc., mentioned above. Constructions aimed at increasing the space factor of the electrical conductors using short conductor segments for the electrical conductors in the stator or aimed at lining up and increasing the density of the coil ends have been proposed in the publication of WO 92/06527 and in Japanese Patent No. 2927288, for example.
FIG. 29
is a side elevation showing part of a stator of a conventional automotive alternator such as described in Japanese Patent No. 2927288, for example,
FIG. 30
is a perspective showing a conductor segment used in the stator of the conventional automotive alternator shown in
FIG. 29
, and
FIGS. 31 and 32
are perspectives from a front end and a rear end, respectively, of part of the stator of the conventional automotive alternator shown in FIG.
29
.
In
FIGS. 29
to
32
, the stator
50
includes: a stator core
51
; a stator winding
52
wound onto the stator core
51
; and insulators
53
mounted inside slots
51
a,
the insulators
53
insulating the stator winding
52
from the stator core
51
. The stator core
51
is a cylindrical laminated core laminated by stacking thin steel plates, and has a number of slots
51
a
extending axially disposed at even pitch circumferentially so as to be open on an inner circumferential side. In this case, ninety-six slots
51
a
are formed so as to house two sets of three-phase winding portions such that the number of slots housing each phase of the winding portions corresponds to the number of magnetic poles (sixteen) in a rotor (not shown). The stator winding
52
is constructed by joining a number of short conductor segments
54
in a predetermined winding pattern.
The conductor segments
54
are formed into a general U shape from an insulated copper wire material having a rectangular cross section, and are inserted two at a time from an axial rear end into pairs of slots
51
a
six slots apart (a pitch of one magnetic pole). Then, end portions of the conductor segments
54
extending outwards at a front end are joined to each other to constitute the stator winding
52
.
More specifically, in pairs of slots
15
a
six slots apart, first conductor segments
54
are inserted from the rear end into first positions from an outer circumferential side within first slots
51
a
and into second positions from the outer circumferential side within second slots
51
a,
and second conductor segments
54
are inserted from the rear end into third positions from the outer circumferential side within the first slots
51
a
and into fourth positions from the outer circumferential side within the second slots
51
a.
Thus, within each slot
15
a,
four straight portions
54
a
of the conductor segments
54
are arranged to line up in a row in a radial direction.
Then, end portions
54
b
of the conductor segments
54
extending outwards at the front end from the first positions from the outer circumferential side within the first slots
51
a
and end portions
54
b
of the conductor segments
54
extending outwards at the front end from the second positions from the outer circumferential side within the second slots
51
a
six slots away in a clockwise direction from the first slots
51
a
are joined to form an outer layer winding having two turns. In addition, end portions
54
b
of the conductor segments
54
extending outwards at the front end from the third positions from the outer circumferential side within the first slots
51
a
and end portions
54
b
of the conductor segments
54
extending outwards at the front end from the fourth positions from the outer circumferential side within the second slots
51
a
six slots away in a clockwise direction from the first slots
51
a
are joined to form an inner layer winding having two turns.
In addition, the inner layer winding and outer layer winding constituted by the conductor segments
54
inserted into the pairs of slots
51
a
six slots apart are connected in series to form one phase of the stator winding
52
having four turns.
A total of six phases of the stator winding
52
each having four turns are formed in this manner. Then, two sets of three-phase stator winding portions are constructed by connecting three phases each of the stator winding
52
into alternating current connections.
In the conventional stator
50
constructed in this manner, at the rear end of the stator core
51
, turn portions
54
c
of the pairs of conductor segments
54
inserted into the same pairs of slots
15
a
are lined up in rows in a radial direction. As a result, the turn portions
54
c
are arranged in two rows circumferentially to constitute a rear-end coil end group.
At the front end of the stator core
51
, on the other hand, joint portions formed by joining the end portions
54
b
of the conductor segments
54
extending outwards at the front end from the first positions from the outer circumferential side within the first slots
51
a
and the end portions
54
b
of the conductor segments
54
extending outwards at the front end from the second positions from the outer circumferential side within the second slots
51
a
six slots away, and joint portions formed by joining the end portions
54
b
of the conductor segments
54
extending outwards at the front end from the third positions from the outer circumferential side within the first slots
51

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