Alternator

Details Alternator Alternator

2000-05-23

2001-07-31

Mullins, Burton S. (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S180000, C310S195000

Reexamination Certificate

active

06268678

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
FIG. 19
is a partial front elevation of a conventional stator mounted in an automotive alternator viewed from an inner circumferential side, and
FIG. 20
is a perspective of part of the conventional stator mounted in an automotive alternator viewed from a front side.
In
FIGS. 19 and 20
, a stator
50
includes: a cylindrical stator core
51
formed with a number of slots
51
a
extending axially at a predetermined pitch in a circumferential direction; a stator winding
52
wound onto the stator core
51
; and insulators
53
installed in each of the slots
51
a
for electrically insulating the stator winding
52
from the stator core
51
. Although not shown, in this conventional example a rotor has 12 poles, and the stator
50
has thirty-six slots
51
a
, which is one slot per pole per phase.
The stator winding
52
is constructed by connecting in series a number of coil segments
55
composed of short lengths of insulated electrical conductor. Each of the coil segments
55
is formed in a general U shape consisting of a pair of leg portions
55
a
joined by a turn portion
55
b.
The coil segments
55
are inserted two at time from a rear end of the stator core into sets of slots
51
a
three slots apart. At that time, four leg portions
55
a
are housed in each slot
51
a
so as to line up in a row in a radial direction. Each of the coil segments
55
on the inner circumferential side is inserted into a first position from the inner circumferential side of a first slot
51
a
and a second position from the inner circumferential side of a second slot
51
a
three slots away, and each of the coil segments
55
on the outer circumferential side is inserted into a third position from the inner circumferential side of the first slot
51
a
and a fourth position from the inner circumferential side of the second slot
51
a
three slots away. In other words, the coil segments
55
are housed in sets of slots
51
a
three slots apart so as to be in different layers.
Next, each of the coil segments
55
is bent such that free ends
55
c
extending outwards from a front end open outwards in a circumferential direction. Then, free ends
55
c
of coil segments
55
extending outwards from the front end from the first position from the inner circumferential side of the slots
51
a
are stacked in a radial direction with the free ends
55
c
of coil segments
55
extending outwards from the front end from the second position from the inner circumferential side of slots
51
a
three slots away, and are joined by soldering or laser welding. Two inner circumferential coils consisting of six coil segments
55
connected in series are thus obtained.
Similarly, free ends
55
c
of coil segments
55
extending outwards from the front end from the third position from the inner circumferential side of the slots
51
a
are stacked in the radial direction with the free ends
55
c
of coil segments
55
extending outwards from the front end from the fourth position from the inner circumferential side of slots
51
a
three slots away, and are joined by soldering or laser welding. Two outer circumferential coils consisting of six coil segments
55
connected in series are thus obtained.
These inner and outer circumferential coils are connected in series to form one phase of coil having 4 turns.
Furthermore, two other phases of coil are also formed in a similar manner.
The stator winding
52
is formed by connecting these three phases of coil into an alternating-current connection.
As shown in
FIGS. 19 and 20
, in the stator
50
constructed in this manner, the coil ends formed by joining the free ends
55
c
of the coil segments
55
to each other are mutually spaced and arranged in neat rows in a circumferential direction and constitute front-end coil end groups
52
a
. The coil ends consisting of the turn portions
55
b
of the coil segments
55
are mutually spaced and arranged in neat rows in a circumferential direction and constitute rear-end coil end groups
52
b.
In the conventional stator
50
, because the front- and rear-end coil end groups
52
a
and
52
b
are constructed by mutually spacing and circumferentially arranging coil ends which connect outside the slots different layers in slots
51
a
three slots apart, axial heights of the front- and rear-end coil end groups
52
a
and
52
b
have been raised and irregularities in the circumferential direction have arisen on the inner circumferential side of the front- and rear-end coil end groups
52
a
and
52
b.
Thus, when this stator
50
is mounted in an alternator, the disadvantages described below arise, and a problem has been that improvements in reliability, increases in performance, and reductions in cost have not been possible.
Namely, there is a risk that foreign matter will infiltrate the coil end groups
52
a
and
52
b
through gaps between the coil ends, damaging the insulation on the electrical conductors and degrading insulation quality.
Furthermore, the longer the axial length of the coil end groups
52
a
and
52
b
, the greater the wind resistance against the cooling air flowing around the coil end groups
52
a
and
52
b
, reducing cooling quality, allowing the temperature of the stator winding
52
to increase excessively.
Also, the longer the axial length of the coil end groups
52
a
and
52
b
, the greater the coil resistance and coil end leakage reactance, reducing output, increasing copper loss, and also reducing efficiency.
Because there are circumferential irregularities on the inner circumferential side of the coil end groups
52
a
and
52
b
, interference noise between the coil end groups
52
a
and
52
b
and the rotor is increased, increasing wind noise.
In addition, the amount of copper constituting the material of the stator winding
52
is increased, causing cost increases.
Moreover, the greater the number of sots per pole per phase, the greater the axial length of the coil end groups, exacerbating the above disadvantages.
SUMMARY OF THE INVENTION
In order to solve the above problems, an object of the present invention is to provide an alternator applicable for automotive use enabling the realization of improved reliability, high performance, and low cost by constructing the coil end groups such that coil ends are arranged in close proximity to one another.
In order to achieve the above object, according to one aspect of the present invention, there is provided an alternator including:
a rotor for forming north-seeking (N) and south-seeking (S) poles along a rotational circumference;
a stator having a cylindrical stator core formed with a number of slots extending axially at a predetermined pitch in a circumferential direction and disposed around an outer circumference of the rotor facing the rotor and a stator winding wound onto the stator core;
a bracket supporting the rotor and the stator;
a rectifier disposed at one end of the rotor; and
a cooling means operating together with rotation of the rotor for forming a passage of cooling air within the bracket for cooling the rotor and the rectifier, the stator winding comprising:
a number of stator winding sub-portions each of which is constituted by insulated strands of wire wound onto the stator core so as to be housed in different layers relative to a slot depth direction within slots a predetermined number of slots apart, the different layers within the slots the predetermined number of slots apart being joined in series outside the slots to constitute coil ends,
wherein each of the coil ends is formed into a connection pattern comprising a pair of root portions extending outwards from the slots the predetermined number of slots apart, a pair of inclined portions bent over and extending circumferentially from the ro

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