Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-04-23
2003-02-04
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S180000, C310S179000, C310S201000, C310S206000, C310S207000
Reexamination Certificate
active
06515393
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive alternator and particularly to a stator winding construction for an automotive alternator.
2. Description of the Related Art
Generally, an automotive alternator includes: a stator constructed by installing a stator winding into a cylindrical stator core in which slots extending axially are formed at a predetermined pitch in a circumferential direction; and a rotor disposed on an inner circumferential side of the stator and having a field winding. The slots are disposed in the stator core at a ratio of one per phase per pole, in proportion to the number of phases in the stator winding and the number of magnetic poles in the rotor.
When the slots are disposed at a ratio of one per phase per pole in this manner, the amount of time that a tooth formed between the slots overlaps an adjacent pair of the magnetic poles.relative to a radial direction is long, leading to increased magnetic flux leakage. This magnetic flux leakage reduces effective magnetic flux and gives rise to surges in the magnetic flux, resulting in fluctuations in the generated voltage and disturbing the output waveform, which causes ripples when the alternating current is converted into direct current.
Thus, an attempt has been proposed in Japanese Patent Laid-Open No. HEI 4-26345, for example, to reduce magnetic flux leakage by disposing the slots at a ratio of two per phase per pole to shorten the amount of time that a tooth overlaps an adjacent pair of the magnetic poles relative to the radial direction.
FIG. 20
is a schematic diagram in which part of a stator such as that described in Japanese Patent Laid-Open No. HEI 4-26345, for example, is developed into a plan.
In
FIG. 20
, a stator core
60
is composed by forming a magnetic steel plate into a cylindrical shape, slots
61
extending axially being disposed therein at an even angular pitch in a circumferential direction at a ratio of two per phase per pole. Here, for twelve magnetic poles in a rotor (not shown), seventy-two slots
61
are disposed in the stator core
60
so as to obtain a stator winding
63
composed of first and second three-phase alternating-current windings. The seventy-two slots
61
are constructed by arranging at a pitch of six slots slot group composed of first to sixth slots
61
a
,
61
a
′, G
1
b
,
61
b
′,
61
c
, and
61
c
′ disposed at a pitch corresponding to an electrical angle of 30° from each other.
A first single-phase winding portion
63
a
is constructed by winding a conductor wire into a wave shape in a first slot group composed of the first slots
61
a
, a third single-phase winding portion
63
b
is constructed by winding a conductor wire into a wave shape in a third slot group composed of the third slots
61
b
, and in addition, a fifth single-phase winding portion
63
c
is constructed by winding a conductor wire into a wave shape in a fifth slot group composed of the fifth slots
61
c
. The first three-phase alternating-current winding is constructed by forming the first, third, and fifth single-phase winding portions
63
a
,
63
b
, and
63
c
wound in this manner into a Y-connection. Here, the slots into which the first, third, and fifth single-phase winding portions
63
a
,
63
b
, and
63
c
are wound have a phase difference corresponding to an electrical angle of 60° from each other.
A second single-phase winding portion
63
a
′ is constructed by winding a conductor wire into a wave shape in a second slot group composed of the second slots
61
a
′, a fourth single-phase winding portion
63
b
′ is constructed by winding a conductor wire into a wave shape in a fourth slot group composed of the fourth slots
61
b
′, and in addition, a sixth single-phase winding portion
63
c
′ is constructed by winding a conductor wire into a wave shape in a sixth slot group composed of the sixth slots
61
c
′. The second three-phase alternating-current winding is constructed by forming the second, fourth, and sixth single-phase winding portions
63
a
′,
63
b
′, and
63
c
′ wound in this manner into a Y-connection. Here, the slots into which the second, fourth, and sixth single-phase winding portions
63
a
′,
63
b
′, and
63
c
′ are wound have a phase difference corresponding to an electrical angle of 60° from each other. Furthermore, the second, fourth, and sixth single-phase winding portions
63
a
′,
63
b
′, and
63
c
′ have a phase difference corresponding to an electrical angle of 30° from the first, third, and fifth single-phase winding portions
63
a
,
63
b
, and
63
c
, respectively.
As shown in
FIG. 21
, a stator
65
is prepared by winding these single-phase winding portions
63
a
,
63
a
′,
63
b
,
63
b
′,
63
c
, and
63
c
′ in the stator core
60
. In the stator
65
constructed in this manner, because the slots
61
are disposed at a ratio of two per phase per pole, portions of a tooth
62
overlapping an adjacent pair of the magnetic poles relative to the radial direction is dramatically reduced. Thus, magnetic flux leakage is reduced, enabling reductions in effective magnetic flux to be suppressed. Similarly, the generation of surges in the magnetic flux is suppressed, reducing fluctuations in the generated voltage and disturbances to the output waveform, thereby reducing ripples when the alternating current is converted into direct current.
In the stator
65
of the conventional automotive alternator, as explained above, the single-phase winding portions
63
a
,
63
a
′,
63
b
,
63
b
′,
63
c
, and
63
c
′ constituting the stator winding
63
are each constructed by winding the conductor wire into a wave shape in every sixth slot
61
so as to extend out of a first slot
61
and enter a second slot
61
six slots away.
As shown in
FIG. 22
, bundles containing a predetermined number of the conductor wires constituting the single-phase winding portions
63
a
,
63
a
′,
63
b
,
63
b
′,
63
c
, and
63
c
′ overlap radially in regions A where the conductor wires are bent circumferentially after extending outwards from the slots
61
, expanding radially.
Thus, coil end groups of the stator winding
63
are formed with large irregularities relative to the circumferential direction, and one problem has been that loud wind noise is generated as a result of pressure differences between the coil end groups and the rotor and between the coil end groups and fans. Furthermore, the radially-overlapping bundles of the conductor wires in the regions A where the conductor wires are bent circumferentially after extending outwards from the slots
61
are less likely to be exposed to a cooling airflow, and therefore another problem has been that heat generated in the stator
65
does not efficiently dissipate from the coil end groups, making it difficult to suppress temperature increases in the stator
65
, and output cannot be improved.
Thus, in a conventional automotive alternator mounted with the stator
65
in which the two three-phase alternating-current windings are wound into the stator core
60
in which slots are disposed at a ratio of two per phase per pole, there have been problems preventing increased performance from the viewpoints of wind noise and output.
SUMMARY OF THE INVENTION
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator enabling temperature increases in a stator to be suppressed by constructing a single-phase winding portion constituting a stator winding by installing a conductor wire which extends from slots such that winds thereof are divided onto first and second circumferential sides, reducing circumferential irregularities in a coil end group to reduce wind noise, and suppressing radial overlap between bundles of winds of the conductor wire constituting the coil end group to raise heat dissipation from the coil end group.
In order to achieve the above obj
Adachi Katsumi
Asao Yoshihito
Oohashi Atsushi
Mitsubishi Denki & Kabushiki Kaisha
Mullins Burton S.
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