Title of Invention

AUTOMOTIVE ALTERNATOR

Abstract Slots are formed in a stator core at a ratio of two slots per phase per pole, and a stator winding is constituted by a first three-phase stator winding and a second three-phase stator winding that are installed in the stator core so as to have a phase difference of 31 to 34 electrical degrees. Stator winding portions that constitute the first three-phase stator winding and the second three-phase stator winding are constituted by distributed windings. Conductor wires that constitute the stator winding portions have^ slot-housed portions that are formed so as to have flat cross sections that are housed inside the slots! and linking portions that are formed so as to have approximately circular cross sections that link end portions of the slot-housed portions to each other, and the slot-housed portions are housed inside the slots in a plurality of layers so as to be arrayed in single columns radially.
Full Text

AUTOMOTIVE ALTERNATOR
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an automotive alternator in which an alternating-current voltage arises in a stator due to rotation of a rotor. Description of the Related Art
In recent years, improvements in power output have been sought in automotive alternators due to increases in vehicle loads, while at the same time automotive vehicle engine compartments are becoming increasingly smaller, leaving little mounting space to spare.
The need for noise reduction is also high, both inside and outside vehicles, and engine noise is being reduced, but noise from automotive alternators that operate constantly to generate electric power in order to supply electric loads to vehicles has become a problem. In automotive alternators that are operated over a comparatively wide range of rotational speeds from low speeds to high speeds, wind noise and electromagnetic noise are considered to be problems. Harmonic wind noise and electromagnetic noise, particularly in a region from an idling state to a normal service region in which engine speed is low, have different frequencies from those of other engine noise and noise from engine auxiliary machinery, and are considered problems because they are noticeable to human ears and are heard as unpleasant noise.
Figure 12 is a longitudinal section of a conventional automotive alternator (hereinafter abbreviated to "alternator"), Figure 13 is a perspective of a rotor of the conventional alternator, Figure 14 is a

perspective of a stator of the conventional alternator, Figure 15 is an electrical circuit diagram for the conventional alternator, and Figure 16 is a plan of a stator core of the conventional alternator. Moreover, output wires and neutral wires of the stator winding have been omitted from Figure 14.
In Figure 12, an alternator includes- a case 3 that is constituted by a front bracket 1 and a rear bracket 2 that are made of aluminum? a shaft 6 that is disposed rotatably inside the case 3 and that has a first end portion to which a pulley 4 is fixed; a Lundell rotor 7 that is fixed to the shaft 61 cooling fans 5 that are fixed to two ends of the rotor 7; a stator 8 that is fixed to an inner wall surface of the case 3; slip rings 9 that are fixed to a second end portion of the shaft 6 so as to supply electric current to the rotor 7; brushes 10 that slide on the slip rings 9! a brush holder 11 that houses the brushes 10; first and second rectifiers 12a and 12b that are electrically connected to the stator 8 so as to convert alternating current that is generated in the stator 8 into direct current; a heatsink 17 that is fitted onto the brush holder 11; and a regulator 18 that is fixed adhesively to the heatsink 17, and that adjusts the magnitude of alternating-current voltage that is generated in the stator 8.
As shown in Figure 13, the rotor 7 includes: a field winding 13 that generates magnetic flux on passage of electric current; and a pole core 51 that covers the field winding 13 such that magnetic poles are formed by the magnetic flux. The pole core 51 includes a first pole core body 20 and a second pole core body 21. The first pole core body 20 and the second pole core body 21 are made of iron, and have claw-shaped magnetic poles 22 and 23 on end portions. The first pole core body 20 and the second pole core body 21 are disposed so as to face each other in such a way that the

clawshaped magnetic poles 22 and 23 alternately intermesh circumferentially, and are fixed to the shaft 6, which is inserted through at central axial positions thereof. Gaps 50 are formed between adjacent clawshaped magnetic poles 22 and 23 so as to prevent magnetic flux from leaking out between the clawshaped magnetic poles 22 and 23 and to constitute cooling passages for cooling the field winding 13.
As shown in Figure 14, the stator 8 includes a stator core 15 and a stator windinsr 16.
The stator core 15 is configured into an annular shape by winding and stacking, or by laminating, a thin steel plate that has been punched into a shape that has indentations and projections at a uniform pitch. As shown in Figure 16, the stator core 15 is constituted by' an annular core back 15a! and teeth 15b that extend radially inward from the core back 15a at a uniform pitch circumferentially. Thus, slots 15c and opening portions 15d of the slots 15c that are defined by the core back 15a and the teeth 15b are arrayed at a uniform angular pitch circumferentially. In this case, seventy-two slots 15c, opening portions 15d, and teeth 15b are formed on the stator core 15 at a uniform angular pitch of 30 electrical degrees. In other words, because the number of magnetic poles in the rotor 7 is twelve poles, the slots 15c are formed at a ratio of two slots per phase per pole.
As shown in Figure 15, the stator winding 16 includes two three-phase stator windings, specifically, a first three-phase stator winding 52 and a second three-phase stator winding 53, in which conducting wires 30 are installed in the stator core 15 so as to have a phase difference of 30 electrical degrees.
The first three-phase stator winding 52 and the second three-phase

stator winding 53 have a front-end coil end group 16f and a rear-end coil end group 16r that respectively project outward from two end surfaces of the stator core 15. The front-end and rear-end coil end groups 16f and 16r are constituted by a plurality of projecting portions 30a that constitute heat-radiating portions. The projecting portions 30a are formed so as to have an identical shape, and are arrayed neatly in two columns so as to be separated from each other circumferentially and radially.
Next, a winding construction of the stator winding 16 will be explained, and to facilitate explanation slot numbers from Slot Number 1 through Slot Number 72 will be allotted to the seventytwo consecutive slots 15c that are formed on the stator core 15.
A first stator winding phase portion 56 is constituted by copper conducting wires 30 that each have an external surface that has been coated with enamel.
The first stator winding phase portion 56 of the first three-phase stator winding 52 is configured by wave winding the conducting wires 30 into every sixth slot 15c from Slot Numbers 1 through 67. Second and third stator winding phase portions of the first three-phase stator winding 52 are similarly configured by wave winding conducting wires 30 into every sixth slot 15c from Slot Numbers 3 through 69 and from Slot Numbers 5 through 71. Four layers of conducting wires 30 are arrayed so as to line up radially in single columns inside each of the slots 15c. The first three-phase stator winding 52 is configured by star-connecting the three stator winding phase portions 56, as shown in Figure 15.
A first stator winding phase portion 56 of the second three-phase stator winding 53 is configured by wave winding conducting wires 30 into every sixth slot 15c from Slot Numbers 2 through 68. Second and third

stator winding phase portions 56 of the second three-phase stator winding 53 are similarly configured by wave winding conducting wires 30 into every sixth slot 15c from Slot Numbers 4 through 70 and from Slot Numbers 6 through 72. Four layers of conducting wires 30 are arrayed so as to line up radially in single columns inside each of the slots 15c. The second three-phase stator winding 53 is configured by star-connecting the three prepared stator winding phase portions 56, as shown in Figure 15.
The first and second three-phase stator windings 52 and 53 are disposed in the slots 15c so as to have a phase difference of 30 electrical degrees, and are electrically connected to the first rectifier 12a and the second rectifier 12b, respectively. Direct-current output from the first and second rectifiers 12a and 12b is connected in parallel and combined.
In automotive alternators that have the above configuration, current is supplied from a battery (not shown) through the brushes 10 and the slip rings 9 to the field winding 13, generating magnetic flux and magnetizing the claw-shaped magnetic poles 22 of the first pole core body 20 into North-seeking (N) poles, and magnetizing the claw-shaped magnetic poles 23 of the second pole core body 21 into South-seeking (S) poles.
At the same time, the pulley 4 is rotated by an engine such that the rotor 7 rotates together with the shaft 6. Because of this, a rotating magnetic field is applied to the first and second three-phase stator windings 52 and 53, giving rise to electromotive force. This alternating-current electromotive force passes through the first and second rectifiers 12a and 12b so as to be converted into a direct current, magnitude thereof is adjusted by the regulator 18, and the battery is charged.

Now, the field winding 13, the stator winding 16, the first and second rectifiers 12a and 12b, and the regulator 18 constantly generate heat during power generation.
Thus, in order to cool the heat that is generated by power generation, air intake apertures la and 2a are disposed through axial end surfaces of the front bracket 1 and the rear bracket 2, and air discharge apertures lb and 2b are disposed through radial side surfaces of the front bracket 1 and the rear bracket 2 so as to face the front-end and rear-end coil end groups 16f and 16r of the stator winding 16.
[0014]
Thus, the cooling fans 5 are driven to rotate together with the rotation of the rotor 7, external air is sucked into the case 3 through the air intake apertures la and 2a, flows axially towards the rotor 7, is then deflected centrifugally by the cooling fans 5, subsequently crosses the front-end and rear-end coil end groups 16f and 16r, and is discharged externally through the air discharge apertures lb and 2b. A cooling airflow also flows through the gaps 50 in the rotor 7 from a front end to a rear end as a result of a pressure difference between the front end and the rear end of the rotor 7.
[0015]
As a result, heat that is generated by the stator winding 16 is radiated from the front-end and rear-end coil end groups 16f and 16r to cooling airflows, suppressing temperature increases in the stator 8. Heat that is generated by the first and second rectifiers 12a and 12b and the regulator 18 is radiated to a cooling airflow by means of heat sinks, thereby suppressing temperature increases in the first and second rectifiers 12a and 12b and the regulator 18. In addition, heat that is generated by the field winding 13 is radiated to the cooling airflow that flows through the

gaps 50 in the rotor 7, thereby suppressing temperature increases in the rotor 7.
In conventional automotive alternators, countermeasures have been taken against output ripples by forming the slots 15c at a ratio of two slots per phase per pole, and by mounting the first three-phase stator winding 52 and the second three-phase stator winding 53 into the stator core 15 so as to be offset by a phase difference of 30 electrical degrees. Moreover, similar technical content is disclosed in Japanese Patent Laid-Open No. HEI 4-26345 (Gazette).
However, in conventional automotive alternators, electromagnetic attraction is generated between the rotor 7 and the stator 8 during power generation due to interaction between the rotating magnetic field, which includes harmonics that originate from the clawshaped magnetic poles 22 and 23 of the rotor 7, and the alternating-current magnetic field, which includes harmonics that originate from the alternating current that is generated by the stator winding 16, and interaction between the rotor 7 and the stator 8 between the rotating magnetic field, which includes harmonics that originate from the clawshaped magnetic poles 22 and 23 of the rotor 7, and permeance harmonics that are generated by the stator slots 15c. This electromagnetic attraction becomes electromagnetic vibrational force in the clawshaped magnetic poles 22 and 23 of the rotor 7 and in the stator core 15, giving rise to vibration, electromagnetic noise, etc.
It is necessary to reduce the electromagnetic vibrational force to reduce such vibrations, noise, etc., and for that purpose it is important to reduce magnetomotive force harmonics and slot harmonics that arise in the stator 8, and it is particularly important to reduce fifth-, seventh*,

eleventh-, and thirteenth-order harmonics that are large in the magnetomotive force harmonics of the stator 8 and eleventh- and thirteenth-order harmonics that are large in the slot harmonics.
In conventional automotive alternators, although the sixth-order harmonic component of the 6f frequency, where f is the fundamental frequency of the output current f, can be reduced as described below, the twelfth-order component is large, and electromagnetic noise that results from the stator slot harmonics is also large because the twelfth-order component of the rotor magnetomotive force harmonics matches the number of slots 15c because the slots 15c are formed at a ratio of two slots per phase per pole. In addition, with regard to wind noise, air interference noise that corresponds to the 12f frequency that results from the slots 15c is also increased, and the wind noise and electromagnetic noise interfere with each other, giving rise to unpleasant noise.
All of the projecting portions 30a that project out of the slots 15c of the stator winding phase portions 56 are wound onto the stator core 15 so as to enter slots 15c that are separated by six slots in a single circumferential direction. Because the bundles of projecting portions 30a are fat, the bundles of projecting portions 30a overlap radially and interfere with each other, increasing irregularities on inner wall surfaces of the coil end groups of the stator winding 16. Thus, loud twelfth-order wind-splitting noise arises as a result of pressure fluctuations between the coil end groups and the rotor 7.
In addition, because the bundles of projecting portions 30a are fat, the area in the coil end groups that is subjected to the cooling airflows is reduced, making heat radiating characteristics of the coil end groups poor.

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 that reduces unpleasant high-frequency noise and wind*splitting noise and that enables cooling of a stator to be improved.
In order to achieve the above object, according to one aspect of the present invention, there is provided an automotive alternator including- a shaft that is rotatably supported by a case! a rotor including: a field winding that generates magnetic flux on passage of electric current; and a pole core that has a plurality of clawshaped magnetic poles disposed circumferentially around the field winding so as to be magnetized by the magnetic flux that is generated by the field winding! and a stator including: a cylindrical stator core in which a plurality of slots that extend axially are formed so as to line up circumferentially, and that is supported by the case so as to envelop the rotor; and a stator winding that is installed in the stator core. The slots are formed in the stator core at a ratio of two slots per phase per pole such that a pitch between radially-extending center lines of adjacent slot opening portions is nonuniform. The stator winding is constituted by a first three-phase stator winding and a second three-phase stator winding that are installed in the stator core so as to have a phase difference of 31 to 34 electrical degrees. Respective winding portions that constitute the first three-phase stator winding and second three-phase stator winding are configured into distributed windings in each of which a conductor wire is installed in the stator core so as to extend outward from two ends of the slots, be distributed in first and second circumferential directions, and enter respective slots that are separated by a predetermined number of slots in

the first and second circumferential directions. The conductor wires have: slot-housed portions that are formed so as to have flat cross sections and that are housed inside the slots; and linking portions that are formed so as to have approximately circular cross sections that link end portions of the slot-housed portions to each other, and the slot-housed portions are housed inside the slots in a plurality of layers so as to be arrayed in single columns radially.
According to the present invention, because the first three-phase stator winding and the second three-phase stator winding are installed in the stator core so as to have a phase difference of 31 to 34 electrical degrees, 12f component electromagnetic noise and wind noise, which is harmonic noise that is extremely unpleasant to the ear, can be reduced, enabling unpleasant noise to be reduced. Decline in output that results from the phase difference can also be kept low.
Because the stator winding portions that constitute the first three-phase stator winding and the second three-phase stator winding are constituted by distributed windings, irregularities on inner surfaces of coil end groups are reduced. Thus, wind noise that arises as a result of pressure fluctuations between the coil end groups and the rotor is reduced. Area in the coil end groups that is subjected to the cooling airflows is also increased, improving the heat radiating characteristics of the coil end groups.
In addition, because the slot-housed portions that are formed so as to have flat cross sections are housed inside the slots in a plurality of layers so as to be arrayed in single columns radially, space factor can be improved, thereby enabling an alternator that has high output to be achieved.
Because the linking portions are formed so as to have approximately circular cross sections, the occurrence of damage to

insulating coatings that results from rubbing among the linking portions is suppressed during installation of the stator winding portions or during shaping of the linking portions after installation of the stator winding portions, improving electrical insulation.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective of a rotor of an automotive alternator according to the present invention!
Figure 2 is an explanatory diagram that shows a stator core in a stator of the automotive alternator according to the present invention flattened out!
Figure 3 is a perspective of the stator of the automotive alternator according to the present invention!
Figure 4 is a partial side elevation of the stator of the automotive alternator according to the present invention!
Figure 5 is a partial cross section that shows a slot-housed state of a stator winding in the stator of the automotive alternator according to the present invention!
Figure 6 is a perspective of a first stator winding phase portion in the stator of the automotive alternator according to the present invention!
Figure 7 is an enlargement of part of the first stator winding phase portion in the stator of the automotive alternator according to the present invention!
Figure 8 is an electrical circuit diagram for the automotive alternator according to the present invention!
Figure 9 is a graph of changes in various rotor magnetomotive force harmonic components!
Figure 10 is a graph of changes in electromagnetic vibrational force

harmonics;
Figure 11 is a graph of relationships among electrical angle phase difference between three-phase stator windings, low-speed output, and noise level;
Figure 12 is a longitudinal section of a conventional automotive alternator;
Figure 13 is a perspective of a rotor of the conventional automotive alternator;
Figure 14 is a perspective of a stator of the conventional automotive alternator;
Figure 15 is an electrical circuit diagram for the conventional automotive alternator; and
Figure 16 is a plan of a stator core of the conventional automotive alternator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will now be explained with reference to the drawings.
Figure 1 is a perspective of a rotor of an automotive alternator according to the present invention, Figure 2 is an explanatory diagram that shows a stator core in a stator of the automotive alternator according to the present invention flattened out, Figure 3 is a perspective of the stator of the automotive alternator according to the present invention, Figure 4 is a partial side elevation of the stator of the automotive alternator according to the present invention, Figure 5 is a partial cross section that shows a slot-housed state of a stator winding in the stator of the automotive alternator according to the present invention, Figure 6 is a perspective of a first stator winding phase portion in the stator of the automotive alternator

according to the present invention, Figure 7 is an enlargement of part of the first stator winding phase portion in the stator of the automotive alternator according to the present invention, and Figure 8 is an electrical circuit diagram for the automotive alternator according to the present invention. Moreover, in each of the figures, portions identical to or corresponding to those in the conventional automotive alternators that are shown in Figures 12 through 16 will be explained using identical numbering.
In Figure 1, a rotor 60 includes" a field winding 13 that generates magnetic flux on passage of electric current; and a pole core 51 that covers the field winding 13 such that magnetic poles are formed by the magnetic flux. The pole core 51 includes a first pole core body 20 and a second pole core body 21. The first pole core body 20 and the second pole core body 21 are made of iron, and have clawshaped magnetic poles 22 and 23 on end portions. The first pole core body 20 and the second pole core body 21 are disposed so as to face each other in such a way that the clawshaped magnetic poles 22 and 23 alternately intermesh circumferentially, and are fixed to the shaft 6, which is inserted through at central axial positions thereof. Gaps 50 are formed between adjacent clawshaped magnetic poles 22 and 23 so as to prevent magnetic flux from leaking out between the clawshaped magnetic poles 22 and 23 and to constitute cooling passages for cooling the field winding 13. Relieved portions 59 are formed on base end portions of side surface portions that are forward in the direction of rotation of the clawshaped magnetic poles 22 and 23.
In Figures 2 through 7, a stator 61 is constituted by: a cylindrical stator core 62; and a stator winding 63 that is installed in the stator core 62. The stator 61 is held between and fitted into a front bracket 1 and a

rear bracket 2 so as to form a uniform air gap between outer circumferential surfaces of claw-shaped magnetic poles 22 and 23 and an inner circumferential surface of the stator core 62.
Next, construction of the stator 61 will be explained in detail.
The stator core 62 is configured into an annular shape by winding and stacking, or by laminating, a thin steel plate that has been punched into a shape that has indentations and projections at a predetermined pitch, in a similar manner to the conventional stator core 15. The stator core 62 is constituted by: an annular core back 62aJ and teeth 62b and 62c that extend radially inward from the core back 62a. The teeth 62b and 62c are disposed so as to alternate circumferentially. Slots 62d are defined by the core back 62a and the teeth 62b and 62c. Pitch between center lines A that pass through the circumferential centers of opening portions 01 and 02 of the slots 62d and extend radially can be changed by changing circumferential widths of adjacent teeth 62b and 62c. In this case, thirty-six pairs of slots 62d in which the pitch between the center lines A is 32.5 electrical degrees are formed at a uniform angular pitch of 60 electrical degrees in the stator core 62. The pitch between the center lines A of adjacent opening portions 01 and 02 alternates between 32.5 electrical degrees and 27.5 electrical degrees. In other words, because the number of magnetic poles in the rotor 60 is twelve poles, the slots 62d are formed at a ratio of two slots per phase per pole.
As shown in Figure 8, two three-phase stator windings, specifically, a first three-phase stator winding 64 and a second three-phase stator winding 65, are installed in the stator core 62 so as to have a phase difference of 32.5 electrical degrees.

The stator winding 63 is constituted by two three-phase stator windings, i.e., the first three-phase stator winding 64 and the second three-phase stator winding 65, in each of which three out of six stator winding phase portions 66 that are made by installing conductor wires 31 in wave shapes in every sixth slot 62d are star-connected.
Each of the stator winding phase portions 66 is constituted by a wave winding in which a conductor wire 31 is wound for a predetermined number of turns, and is formed into a distributed winding that has a wave-shaped pattern that is constituted by twelve slot-housed portions 66a that are arrayed at a pitch of six slots, and linking portions 66b that link a first half of the end portions of adjacent slot-housed portions 66a with each other alternately at first and second axial ends and that link a second half of the end portions with each other alternately at second and first axial ends.
The stator winding phase portions 66 are installed in the stator core 62 such that the slot-housed portions 66a are housed in respective slots 62d that are arrayed at a pitch of six slots. The six stator winding phase portions 66 are installed in the stator core 62 so as to be offset by one slot (IP) circumferentially from each other and so as to be stacked radially in six layers. The linking portions 66b of the six stator winding phase portions 66 constitute front-end and rear-end coil end groups 63f and 63r of the stator winding 63.
The conductor wires 31 are conductor wires that are made of a copper wire material that has been coated with an insulator such as enamel, etc., portions that correspond to the slot-housed portions 66a of the stator winding phase portions 66 being formed so as to have flat cross sections such as rectangular cross sections, for example, and portions that

correspond to the linking portions 66b being formed so as to have circular cross sections. In addition, as shown in Figure 7, slot opening passing portions 66c are configured by deforming boundary portions between the slot-housed portions 66a and the linking portions 66b of the conductor wires 31 so as to have flat cross sections. The slot opening passing portions 66c are formed so as to have a radial thickness equivalent to that of the slot-housed portions 66a and a circumferential length that is shorter than the opening portions 01 and 02 of the slots 62d.
As shown in Figure 5, the slot-housed portions 66a are housed in six layers with longitudinal axes of their flat cross sections aligned circumferentially so as to line up in single columns radially in slots 62d into which insulators 32 have been mounted. Wedges 34 are fitted into the opening portions 01 and 02 of the slots 62d such that the slot-housed portions 66a are pressed toward bottom surfaces of the slots 62d. Thus, the slot-housed portions 66a are placed in close contact with each other, and the slot-housed portions 66a in the outermost layer are in close contact with the bottom surfaces of the slots 62d with the insulators 32 interposed. In addition, varnish 33 is impregnated into the slots 62d so as to firmly fix the stator core 62 and the stator winding 63.
An automotive alternator according to the present invention is configured in a similar manner to the conventional automotive alternator except for the fact that the rotor 60 and the stator 61 are used instead of the rotor 7 and the stator 8.
According to this embodiment, the slot-housed portions 66a of the conductor wires 31 that are housed in the slots 62d are formed so as to have flat cross sections. The slot-housed portions 66a that have the flat

cross sections are housed in the slots 62d so as to be arrayed in single columns radially. Thus, space factor is improved, enabling alternator output to be increased. In addition, because the slot-housed portions 66a are housed inside the slots 62d without gaps, rubbing between the conductor wires 31 and wall surfaces of the slots 62d that results from mechanical vibration is suppressed, suppressing the occurrence of damage to the insulating coatings on the conductor wires 31.
The slot-housed portions 66a that have the flat cross sections are housed in the slots 62d so as to be arrayed in single columns radially, and the varnish 33 is impregnated into the slots 62d. The slot-housed portions 66a are thereby fixed to the stator core 62, eliminating rubbing among the slot-housed portions 66a and rubbing between the slot-housed portions 66a and the stator core 62, thereby suppressing deterioration of electrical insulation that accompanies damage to insulating coatings on the slot-housed portions 66a. In addition, because the rigidity of the stator 61 is increased, the occurrence of electromagnetic noise is suppressed.
Now, in the above embodiment, an insulating resin such as a varnish, etc., may also be applied to the front-end and rear-end coil end groups 63f and 63r. In that case, because the insulating resin fixes the linking portions 66b to each other and rubbing among the linking portions 66b that results from vibration is eliminated, deterioration of electrical insulation that accompanies damage to insulating coatings on the linking portions 66b is suppressed. At the same time, because the rigidity of the stator 61 is also increased, the occurrence of mechanical vibration is suppressed.
Inner circumferential linking portions 66b are more likely to be

cooled by the cooling fans 5, and outer circumferential linking portions 66b are less likely to be cooled by the cooling fans 5. However, because the slot-housed portions 66a are placed in close contact with each other, heat transfer occurs easily between the slot-housed portions 66a, making the temperature of the slot-housed portions 66a uniform. Thus, excessive local temperature increases are suppressed in the stator winding 63.
Because the slot-housed portions 66a in the outermost layers are placed in close contact with the bottom surfaces of the slots 62d with the insulators 32 interposed, heat from the stator winding 63 is transferred to the stator core 62 efficiently, suppressing excessive temperature increases in the stator winding 63.
Because the slot opening passing portions 66c are formed at the boundary portions between the slot-housed portions 66a and the linking portions 66b, the slot opening passing portions 66c move axially through the 01 and 02 of the slots 62d as the stator winding phase portions 66 are being mounted from an axial direction relative to the stator core 62, leading the slot-housed portions 66a into the slots 62d. Thus, mountability of the stator winding 63 into the stator core 62 is improved, and contact between the conductor wires 31 and the stator core 62 can be avoided as the stator winding phase portions 66 are being mounted to the stator core 62, suppressing the occurrence of damage to the insulating coating of the conductor wires 31.
Because the linking portions 66b are formed so as to have circular cross sections, the occurrence of damage to insulating coatings on the conductor wires 31 that results from rubbing among the linking portions 66b is suppressed when the stator winding phase portions 66 are being installed in the stator core 62, and when the linking portions 66b are being

shaped after the stator winding phase portions 66 have been installed in the stator core 62. Here, it is not necessary for the cross-sectional shapes of the linking portions 66b to be perfect circles; they may also be ellipses.
Because the stator winding phase portions 66 that constitute the stator winding 63 are each constituted by a distributed winding, the linking portions 66b (the coil end groups) of the stator winding phase portions 66 that project out of the slots 62d are distributed half each in first and second circumferential directions. Thus, because the bundles of linking portions 66b are slenderer, bending stresses that act on the linking portions 66b as a result of the bundles of the linking portions 66b interfering with each other when stacked radially are reduced. Thus, even if such bending stresses are concentrated at the boundary portions between the slot-housed portions 66a and the linking portions 66b, insulating coatings at the boundary portions are less likely to be damaged, suppressing the occurrence of incidents of short-circuiting among the conductor wires 31. In addition, because the bundles of linking portions 66b are slenderer, the area in the front-end and rear-end coil end groups 63f and 63r that is subjected to the cooling airflows is increased, improving heat radiating characteristics of the front-end and rear-end coil end groups 63f and 63r.
Because radial overlap between the bundles of linking portions 66b is dispersed circumferentially, irregularities on inner wall surfaces of the front-end and rear-end coil end groups 63f and 63r are reduced. Wind noise arising as a result of pressure fluctuations between the front-end and rear-end coil end groups 63f and 63r and the rotor 7 or between the front-end and rear-end coil end groups 63f and 63r and the cooling fans 5 is thereby reduced. Specifically, increases in twelfth-order wind-splitting noise can be suppressed.

Because the relieved portions 59 are formed on the base end portions of the side surface portions that are forward in the direction of rotation of the claw-shaped magnetic poles 22 and 23, pressure fluctuations in the air gap between the rotor 60 and the stator 61 are reduced, enabling twelfth-order wind-splitting noise that is generated there to be reduced.
Next, the electrical angle phase difference a between the first three-phase stator winding 64 and the second three-phase stator winding 65 will be investigated. The slots 62d are formed in the stator core 62 at a ratio of two slots per phase per pole. In other words, since the number of magnetic poles in the rotor 60 is twelve poles, thirty-six pairs of slots 62d in which the pitch between the center lines A is a electrical degrees are formed at a uniform angular pitch of 60 electrical degrees. The pitch between the center lines A (electrical angle a) can be set arbitrarily by changing the circumferential widths of the teeth 62b and 62c. The pitch between Slot Number 1 of the slots 62d and Slot Number 2 of the slots 62d is a electrical degrees, and the pitch between Slot Number 2 of the slots 62d and Slot Number 3 of the slots 62d is (60 - a) electrical degrees.
The first three-phase stator winding 64 is prepared by star-connecting the stator winding phase portion 66 that has been installed in Slot Numbers 1, 7, 13, etc., through 67 of the slots 62d, the stator winding phase portion 66 that has been installed in Slot Numbers 3, 9, 15, etc., through 69 of the slots 62d, and the stator winding phase portion 66 that has been installed in Slot Numbers 5, 11, 17, etc., through 71 of the slots 62d.
Similarly, the second three-phase stator winding 65 is prepared by star-connecting the stator winding phase portion 66 that has been installed

in Slot Numbers 2, 8, 14, etc., through 68 of the slots 62d, the stator winding phase portion 66 that has been installed in Slot Numbers 4, 10, 16, etc., through 70 of the slots 62d, and the stator winding phase portion 66 that has been installed in Slot Numbers 6, 12, 18, etc., through 72 of the slots £9A
Output wires and neutral points N of the first and second three-phase stator windings 64 and 65 that have been prepared in this manner are electrically connected to the first rectifier 12a and the second rectifier 12b, as shown in Figure 8. Direct-current output from the first and second rectifiers 12a and 12b is connected in parallel and combined. Here, the electrical angle phase difference between the first three-phase stator winding 64 and the second three-phase stator winding 65 is a degrees.
Now, during power generation, electromagnetic attraction is generated between the rotor 60 and the stator 61 due to interaction between the rotating magnetic field, which includes harmonics that originate from the claw-shaped magnetic poles 22 and 23 of the rotor 60, and the alternating-current magnetic field, which includes harmonics that originate from the alternating current that is generated by the stator winding 63. This electromagnetic attraction becomes electromagnetic vibrational force in the claw-shaped magnetic poles 22 and 23 of the rotor 60 and in the stator core 62, giving rise to vibration and electromagnetic noise.
Regarding this electromagnetic vibrational force, the present inventors performed electromagnetic field analysis on automotive alternators in which two three-phase stator windings were in parallel and

the number of slots of the stator was six times the number of poles. It was found that electromagnetic noise in an automotive alternator results from electromagnetic vibrational force in the order of three times and in the order of six times the number of poles in one revolution. In other words, it results from electromagnetic vibrational force at a 6f frequency and a 12f frequency, where f is the fundamental frequency of the output current f.
In the stator magnetomotive force harmonics, since the phase of each of the phase currents depends on slot opening portion pitch, the harmonics that are shown in Figure 9 arise if the stator magnetomotive force harmonics are calculated for various slot opening portion pitches.
Since the orientation of the stator magnetomotive force harmonics and the orientation of the rotor magnetomotive force harmonics are in inverse relationships, the fifth orders together, the seventh orders together, etc., form standing waves. However, in some cases, since a sixth-order electromagnetic force made by the fifth orders together and a sixth-order electromagnetic vibrational force made by the seventh orders together may cancel each other out, it is necessary to allow for phase when adding them together.
The relative values of sixth-order electromagnetic vibrational force and twelfth-order electromagnetic vibrational force that can be calculated from these results are shown in Figure 10.
From Figure 10, it can be seen that the sixth-order electromagnetic
vibrational force is smallest at a uniform pitch of 30 degrees, and increases
proportionately as the pitch is increased. The twelfth-order
electromagnetic vibrational force is greatest at a uniform pitch of 30 degrees, and decreases in inverse proportion as the pitch is increased. It can also be seen that the crossover point of the electromagnetic vibrational

forces is approximately 31 degrees.
Consequently, although offsetting the phase difference (electrical angle a) between the three-phase stator windings slightly from 30 degrees, i.e., to a nonuniform pitch, increases the sixth-order electromagnetic vibrational force, the twelfth-order electromagnetic vibrational force, which causes unpleasant harmonic noise, is reduced.
In order to make the pitch of the slot opening portions nonuniform, wide teeth and narrow teeth are formed alternately, and if the pitch is made extremely nonuniform, magnetic saturation arises in the narrow teeth, reducing the amount of magnetic flux that flows to the narrow teeth from the claw-shaped magnetic poles. Output is particularly reduced at low-speed rotation (during idling) when the rotational frequency of the rotor 60 is 2,000 rpm. In the case of full-wave rectification by three-phase connections, output from the first three-phase stator winding and the second three-phase stator winding is balanced, and output ripples are also lower, when the phase difference is 30 electrical degrees, and thus output ripples will worsen the further the phase is offset.
Figure 11 is a graph of respective relationships between electrical angle phase difference between a first three-phase stator winding and a second three-phase stator winding, low-speed output, and noise level during power generation that were found by the present inventors in experiments using an automotive alternator in a 100 A class.
From Figure 11, it can be seen that when the electrical angle phase difference between the three-phase stator windings is in a range of 31 to 34 degrees, noise level is low, and low-speed output is high. When manufacturing error in the slots of the stator is taken into account, 32.5 degrees is optimal, being the median.

Thus, in the present automotive alternator, by offsetting the electrical angle phase difference between the first three-phase stator winding 64 and the second three-phase stator winding 65 from 30 degrees, the 12f electromagnetic vibrational force, which is extremely unpleasant to the ear, can be reduced, and electromagnetic noise can also be reduced. From Figure 11, it can be seen that in order to lower the noise level and increase low-speed output, it is desirable to set the electrical angle phase difference between the first three-phase stator winding 64 and the second three-phase stator winding 65 within a range of 31 to 34 degrees, and considering manufacturing error in the stator, it is even more desirable to set the electrical angle phase difference to 32.5 degrees.
By offsetting the electrical angle phase difference between the first three-phase stator winding 64 and the second three-phase stator winding 65 from 30 degrees, circumferential widths of flange portions at tip end portions of adjacent teeth 62b and 62c become unequal. Thus, pressure fluctuations in the air gap between the stator 61 and the rotor 60 are dispersed, enabling wind noise that is generated there also to be reduced. Consequently, since mutual interference between electromagnetic noise and wind noise is also reduced, the noise level that is generated by the alternator is reduced, suppressing noise that is sensed by passengers. However, although the degree of contribution to the noise is low if the electrical angle phase difference is greater than 34 degrees, the noise level has a tendency to worsen since other harmonic components become excessive.
Because the neutral points N of the first three-phase stator winding 64 and the second three-phase stator winding 65 are electrically connected

to the first and second rectifiers 12a and 12b, respectively, output can be extracted from the neutral point voltages when the alternator is rotating at high speed, enabling output to be improved without worsening noise.
Because the first rectifier 12a is electrically connected to the first three-phase stator winding 64, the second rectifier 12b is electrically connected to the second three-phase stator winding 65, and the outputs from each are combined after rectification, the outputs from the three-phase stator winding 64 and 65 are output stably without affecting each other. This is particularly effective in cases where the combined output is large and the temperature of the diodes that constitute a rectifier would exceed permissible temperatures in a single rectifier.
Moreover, in the above embodiment, the relieved portions 59 were disposed on the base end portions of the side surface portions that are forward in the direction of rotation, but relieved portions may also be disposed rearward in the direction of rotation. In that case, because the magnetic flux density distribution in the air gap is made uniform, and the magnetic flux that originates from the field winding 13 approaches an ideal sine wave, the amount of magnetic flux increases, improving low~speed output.
In the above embodiment, an automotive alternator in which the total number of slots is seventy-two and the total number of claw-shaped magnetic poles is twelve has been explained, but the present invention can of course also be applied to automotive alternators in which the total number of slots is ninety-six and the total number of claw-shaped magnetic poles is sixteen, or the total number of slots is 120 and the total number of clawshaped magnetic poles is twenty, for example.
In the above embodiment, windings were configured using

conductor wires 31 that were continuous wires, but windings may also be configured by respectively connecting a large number of "U"-shaped conductor segments.
In the above embodiment, the field winding 13 was encompassed by the rotor 60, but the present invention can also be applied to alternators in which a field winding is fixed to a case, and magnetic poles are formed by supplying magnetic flux to the pole core of the rotor across an air gap. The present invention is, of course, not limited only to automotive alternators.



WHAT IS CLAIMED IS:
1. An automotive alternator comprising:
a shaft that is rotatably supported by a case! a rotor comprising:
a field winding that generates magnetic flux on passage of electric current; and
a pole core that has a plurality of claw-shaped magnetic poles disposed circumferentially around said field winding so as to be magnetized by said magnetic flux that is generated by said field winding; and a stator comprising:
a cylindrical stator core in which a plurality of slots that extend axially are formed so as to line up circumferentially and that is supported by said case so as to envelop said rotor! and a stator winding that is installed in said stator core, characterized in that:
said slots are formed in said stator core at a ratio of two slots per phase per pole such that a pitch between radially-extending center lines of adjacent slot opening portions is nonuniform;
said stator winding is constituted by a first three-phase stator winding and a second three-phase stator winding that are installed in said stator core so as to have a phase difference of 31 to 34 electrical degrees;
respective winding portions that constitute said first three-phase stator winding and second three-phase stator winding are configured into distributed windings in each of which a conductor wire is installed in said stator core so as to extend outward from two ends of said slots, be distributed in first and second circumferential directions, and enter respective slots that are separated by a predetermined number of slots in said first and second circumferential directions;

said conductor wires have:
slot-housed portions that are formed so as to have flat cross sections and that are housed inside said slots! and
linking portions that are formed so as to have approximately circular cross sections that link end portions of said slot-housed portions to each other; and said slot-housed portions are housed inside said slots in a plurality of layers so as to be arrayed in single columns radially
2. An automotive alternator according to Claim 1, wherein said phase
difference between said first three-phase stator winding and said second
three-phase stator winding is 32.5 electrical degrees.
3. An automotive alternator according to Claim 1, wherein cooling
fans are fixed to axial end surfaces of said rotor.


Documents:

969-CHE-2007 AMENDED CLAIMS 26-07-2010.pdf

969-CHE-2007 EXAMINATION REPORT REPLY RECEIVED 26-07-2010.pdf

969-che-2007 form 3 02-08-2010.pdf

969-CHE-2007 POWER OF ATTORNEY 26-07-2010.pdf

969-che-2007-abstract.pdf

969-che-2007-claims.pdf

969-che-2007-correspondnece-others.pdf

969-che-2007-description(complete).pdf

969-che-2007-drawings.pdf

969-che-2007-form 1.pdf

969-che-2007-form 18.pdf

969-che-2007-form 3.pdf


Patent Number 244916
Indian Patent Application Number 969/CHE/2007
PG Journal Number 53/2010
Publication Date 31-Dec-2010
Grant Date 24-Dec-2010
Date of Filing 07-May-2007
Name of Patentee MITSUBISHI ELECTRIC CORPORATION
Applicant Address 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310,JAPAN
Inventors:
# Inventor's Name Inventor's Address
1 KASHIHARA, TOSHIAKI C/O MITSUBISHI ELECTRIC CORPORATION 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310,JAPAN
PCT International Classification Number H02K19/22
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA