Title of Invention

AUTOMOTIVE ALTERNATOR

Abstract Tooth portions of a stator core are formed such that a radial length ht and a width bt satisfy an expression 0.15 < bt/ht < 0.4. The stator winding has a plurality of winding portions that are installed in respective slot groups that are constituted by slots of the stator core that are separated by a predetermined number of slots. Each of the winding portions is configured by winding a conductor wire in a distributed winding in the slot groups so as to extend outward from two ends of the slots, be distributed in first and second circumferential directions, and enter each of the slots that are separated by the predetermined number of slots in the first and second circumferential directions. In addition, slot-housed portions of the conductor wire are housed inside the slots in a plurality of layers with longitudinal axes of flat cross sections aligned circumferentially so as to be arrayed in single columns radially.
Full Text

AUTOMOTIVE ALTERNATOR
BACKGROUND OF THE INVENTION
Field of the Invention
[0001]
The present invention relates to an automotive alternator, and particularly relates to an automotive alternator in which cooling of a stator is increased by allowing a cooling airflow to pass through a cooling airflow ventilation channel that is formed by a coil end group of a stator winding and tooth portions of a stator core.
Description of the Related Art
[0002]
Figure 16 is a cross section of a conventional automotive alternator, Figure 17 is a perspective of a stator that is used in the conventional automotive alternator, Figure 18 is a schematic diagram that explains a conventional method for manufacturing a stator core, and Figure 19 is a plan of a conventional stator core.
[0003]
In Figures 16 and 17, a conventional automotive 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 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 6; cooling fans 5 that are fixed to two axial end portions of the rotor 7; a stator 8 that is fixed to the case 3 so as to envelop the rotor 1\ 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; a pair of brushes 10 that slide on surface of the slip rings 9; a brush holder 11 that houses the brushes 10; a rectifier 12 that is electrically connected to the stator 8 so as to convert alternating current that is generated in the stator

8 into direct current; and a regulator 18 that is mounted to a heatsink 17 that is fitted onto the brush holder 11, and that adjusts the magnitude of alternating-current voltage that is generated in the stator 8.
[0004]
The rotor 7 includes- a field winding 13 that generates magnetic flux on passage of electric current; and first and second pole cores 20 and 21 that are disposed so as to cover the field winding 13 such that magnetic poles are formed by the magnetic flux. The first and second pole cores 20 and 21 are made of iron, each has a plurality of first and second clawshaped magnetic poles 22 and 23 that have an approximately trapezoidal outermost diameter surface shape disposed on an outer circumferential edge portion at a uniform angular pitch circumferentially so as to project axially, and the first and second pole cores 20 and 21 are fixed to the shaft 6 so as to face each other such that the first and second claw-shaped magnetic poles 22 and 23 intermesh with each other.
[0005]
The stator 8 is constituted by: a cylindrical stator core 15 in which slots 33 that extend parallel to an axial direction are disposed at a uniform angular pitch circumferentially; and a stator winding 16 that is wound into the slots 33 of the stator core 15. The stator winding 16 is constituted by three phases of wave winding that are formed by winding a conductor wire 29 that functions as an electrical conductor that is made of a copper wire material that has a circular cross section that is coated with an insulator into wave shapes in every third slot 33. Each of the phases of wave winding are wound onto the stator core 15 such that the slots 33 into which they are wound are offset by one slot from each other. In addition, each of the phases of wave winding is formed by winding the conductor wire 29 into a distributed winding. The stator 8 is held between the front bracket 1 and the rear bracket 2 so as to form a uniform air gap between outer

surfaces of the clawshaped magnetic poles 22 and 23 and an inner surface of the stator core 15.
Moreover, the number of magnetic poles in the rotor 7 is twelve, and thirty-six slots 33 are formed in the stator core 15. In other words, the number of slots per phase per pole is one. The stator winding 16 is formed into a three-phase alternating-current winding in which the three phases of wave winding are formed into an alternating-current connection (such as a wye connection, for example).
[0006]
A method for manufacturing the stator core 15 will now be explained with reference to Figure 18.
First, a long magnetic steel plate 30 is supplied to a pressing machine (not shown) to form tooth portions 30a and a base portion 30b. Next, the magnetic steel plate 30 is supplied to a core manufacturing apparatus (not shown). There, pins 34 are intermeshed with gaps 30c that are defined by the tooth portions 30a and the base portion 30b, as shown in Figure 18, and the magnetic steel plate 30 is bent, wound, and stacked into a helical shape. Then, the magnetic steel plate 30 is cut after being laminated to a predetermined thickness. Outer circumferential portions of the magnetic steel plate 30 that has been wound and stacked in this manner are welded to obtain the stator core 15 that is shown in Figure 19. Here, the tooth portions 30a and the base portion 30b are respectively superposed in the direction of lamination in the magnetic steel plate 30 that has been wound and stacked.
[0007]
As shown in Figure 19, the stator core 15 that has been prepared in this manner includes: a cylindrical base portion 32; tooth portions 31 that are each disposed so as to extend toward a central axis from an inner circumferential surface of the base portion 32; and slots 33 that are defined

by the base portion 32 and adjacent tooth portions 31. The tooth portions 31 are arrayed at a uniform angular pitch on the inner circumferential surface of the base portion 32.
[0008]
In a conventional automotive alternator that has been configured in this manner, an electric current is supplied from a battery (not shown) through the brushes 10 and the slip rings 9 to the field winding 13, generating a magnetic flux. The first claw-shaped magnetic poles 22 on the first pole core 20 are magnetized into North-seeking (N) poles by this magnetic flux, and the second clawshaped magnetic poles 23 on the second pole core 21 are magnetized into South-seeking (S) poles.
At the same time, the pulley 4 is driven by an engine such that the rotor 7 is rotated by the shaft 6. A rotating magnetic field is applied to the stator core 15 due to the rotation of the rotor 7, generating an electromotive force in the stator winding 16. Alternating electromotive force generated in the stator winding 16 is converted into direct current by the rectifier 12, the magnitude of the output voltage thereof is adjusted by the regulator 18, and the battery is recharged.
[0009]
Now, the field winding 13, the stator winding 16, the rectifier 12, and the regulator 18 constantly generate heat during power generation, and in an automotive alternator that has a rated output current of 100A, the quantity of heat generated is 60W, 500W, 120W, and 6W, respectively, at rotation points that are thermally high.
Thus, in order to cool the heat 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 coil end groups 16f and 16r of the stator

winding 16.
Thus, the cooling fans 5 are driven to rotate together with the rotation of the rotor 7, and cooling airflow channels are formed in which 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 coil end groups 16f and 16r, and is discharged externally through the air discharge apertures lb and 2b. A cooling airflow channel is also formed in which cooling air flows through the inside of 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.
As a result, heat generated in the stator winding 16 is radiated from the coil end groups 16f and 16r to cooling airflows, suppressing temperature increases in the stator 8. Heat generated in the rectifier 12 and the regulator 18 is radiated to a cooling airflow by means of heat sinks 12a and 17, thereby suppressing temperature increases in the rectifier 12 and the regulator 18. In addition, heat generated in the field winding 13 is dissipated to a cooling airflow that flows through the inside of the rotor 7, thereby suppressing temperature increases in the rotor 7.
[0010]
In a conventional automotive alternator that has been configured in this manner, it is important to suppress temperature increases in the stator winding 16, which constitutes the largest heat-generating part. Since the cooling airflows that are formed by the cooling fans 5 and the rotor 7 pass through the coil end groups 16f and 16r of the stator winding 16 from an inner circumferential side in a radial direction, heat generated in the stator winding 16 is radiated from the coil end groups 16f and 16r to the cooling airflows, suppressing temperature increases in the stator 8.
[0011]
Now, in an actual machine, the ambient temperature may be 90

degrees Celsius under the worst operating conditions. Furthermore, the softening temperature of a varnish that is impregnated into the slots 33 of the stator core 15 to bond the stator core 15 and the stator winding 16 is 230 degrees Celsius. Thus, when consideration is given to decreases in output that result from field current decreases due to ambient temperature increases, the temperature of the stator 8 will be prevented from exceeding the varnish softening temperature even under the worst operating conditions if the temperature increase at an ambient temperature of 90 degrees Celsius is suppressed to less than or equal to 140 degrees Celsius. A temperature increase of 140 degrees Celsius at an ambient temperature of 90 degrees Celsius corresponds to a temperature increase of 170 degrees Celsius at an ambient temperature of 20 degrees Celsius.
If the varnish reaches the softening temperature, heat degradation is accelerated and bonding between the stator core 15 and the stator winding 16 is loosened. Looseness in the bonding between the stator core 15 and the stator winding 16 gives rise to abrasion between the conductor wires 29 in the stator winding 16 and the stator core 15, damaging insulating coatings on the conductor wires 29 and making electrical insulation poor.
[0012]
Thus, the present applicants have focused on ventilation channels that allow air to pass through gaps between coil end groups 16f and 16r of the stator winding 16 and end surfaces of the stator core 15, and have found that a ratio (bt/ht) between width bt and radial length ht of the tooth portions 31 that define these ventilation channels influences the cooling of the stator winding 16.
[0013]
However, until now no consideration has been given to the ratio (bt/ht) between the width bt and the radial length ht of the tooth portions

31. Thus, as shown in Figure 20, stator cores 15 in which bt/ht is approximately equal to 0.42 (bt - 4.8 mm; ht = 11.4 mm), for example, have been used in conventional automotive alternators. When such automotive alternators were made to generate power under full load and saturation temperature of the stator 8 was measured with output stable, the increase in the saturation temperature from the experimental ambient temperature (20°C) was calculated to be 173 degrees Celsius. Consequently, one problem in conventional automotive alternators has been that the temperature of the stator 8 exceeds the varnish softening temperature under the worst operating conditions, accelerating heat degradation and making electrical insulation poor.
SUMMARY OF THE INVENTION
[0014]
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator that can suppress deterioration of electrical insulation by improving heat degradation resistance and that can also improve cooling by improving heat radiating characteristics of a stator winding by setting a ratio (bt/ht) between width bt and radial length ht of tooth portions appropriately to improve the heat radiating characteristics of the stator winding and to keep stator temperature below a varnish softening temperature even under the worst operating conditions.
[0015]
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 that is fixed to the shaft and that has^ a field winding that generates magnetic flux on passage of electric current; and a plurality of claw-shaped magnetic poles that are

arrayed circumferentially around the field winding so as to be magnetized by the magnetic flux that is generated by the field winding; a stator that has- 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; and a cooling fan that is fixed to an axial end surface of the rotor. The stator core is configured by laminating a magnetic steel plate, and has: a cylindrical base portion! a plurality of tooth portions that are disposed so as to extend toward a central axis from the base portion! and the plurality of the slots that are defined by the base portion and adjacent tooth portions, ventilation channels through which cooling airflows pass from radially inside due to rotation of the rotor are formed by coil end groups of the stator winding and the tooth portions of the stator core, and the tooth portions are formed such that a radial length ht and a width bt satisfy an expression 0.15 [0016]
According to the present invention, because the ventilation

channels through which cooling airflows pass from radially inside due to rotation of the rotor are formed by the coil end groups of the stator winding and the tooth portions of the stator core, and the tooth portions are formed such that the radial length ht and the width bt satisfy an expression 0.15 Because each of the winding portions of the stator winding is wound in a distributed winding, the area in the coil end groups that is subjected to the cooling airflows is increased, improving the heat radiating characteristics of the coil end groups.
In addition, because the slot-housed portions are housed inside the slots in a plurality of layers with longitudinal axes of the flat cross sections aligned circumferentially so as to be arrayed in single columns radially, improvements in space factor can be achieved, enabling an alternator that has high output to be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017]
Figure 1 is a cross section of an automotive alternator according to Embodiment 1 of the present invention;
Figure 2 is a perspective of a stator of the automotive alternator according to Embodiment 1 of the present invention;
Figure 3 is a partial cross section that shows a slot-housed state of a stator winding in the stator of the automotive alternator according to Embodiment 1 of the present invention;
Figure 4 is a partial side elevation of the stator of the automotive alternator according to Embodiment 1 of the present invention;
Figures 5A, 5B, and 5C are process diagrams that explain a process

for manufacturing a star-shaped winding unit in a method for manufacturing the stator of the automotive alternator according to Embodiment 1 of the present invention;
Figure 6 is a perspective of a distributed winding unit in the stator of the automotive alternator according to Embodiment 1 of the present invention!
Figure 7 is a partial enlargement of the distributed winding unit in the stator of the automotive alternator according to Embodiment 1 of the present invention;
Figure 8 is a process diagram that explains a process for mounting the distributed winding unit to a stator core in the method for manufacturing the stator of the automotive alternator according to Embodiment 1 of the present invention;
Figure 9 is a graph that shows a relationship between bt/ht of the stator core and stator temperature increase in the automotive alternator according to Embodiment 1 of the present invention!
Figure 10 is a perspective of a stator of an automotive alternator according to Embodiment 2 of the present invention;
Figure 11 is a partial side elevation of the stator of the automotive alternator according to Embodiment 2 of the present invention;
Figure 12 is a partial cross section that shows a slot-housed state of a stator winding in the stator of the automotive alternator according to Embodiment 2 of the present invention!
Figure 13 is a perspective of a single winding phase portion in the stator of the automotive alternator according to Embodiment 2 of the present invention!
Figure 14 is an enlargement of part of the single winding phase portion in the stator of the automotive alternator according to Embodiment 2 of the present invention;

Figure 15 is a cross section of an automotive alternator according to
Embodiment 3 of the present invention;
Figure 16 is a cross section of a conventional automotive alternator** Figure 17 is a perspective of a stator that is used in the
conventional automotive alternator;
Figure 18 is a schematic diagram that explains a conventional
method for manufacturing a stator core;
Figure 19 is a plan of a conventional stator core; and
Figure 20 is a partially-enlarged plan of the conventional stator
core.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018]
Preferred embodiments of the present invention will now be explained with reference to the drawings. Embodiment 1
Figure 1 is a cross section of an automotive alternator according to Embodiment 1 of the present invention, Figure 2 is a perspective of a stator of the automotive alternator according to Embodiment 1 of the present invention, Figure 3 is a partial cross section that shows a slot-housed state of a stator winding in the stator of the automotive alternator according to Embodiment 1 of the present invention, Figure 4 is a partial side elevation of the stator of the automotive alternator according to Embodiment 1 of the present invention, Figures 5A, 5B, and 5C are process diagrams that explain a process for manufacturing a star-shaped winding unit in a method for manufacturing the stator of the automotive alternator according to Embodiment 1 of the present invention, Figures 6 and 7 are a perspective and a partial enlargement, respectively, of a distributed winding unit in the stator of the automotive alternator according to

Embodiment 1 of the present invention, and Figure 8 is a process diagram that explains a process for mounting the distributed winding unit to a stator core in the method for manufacturing the stator of the automotive alternator according to Embodiment 1 of the present invention. Moreover, in each of the figures, identical numbering will be given to portions identical to or corresponding to those in the conventional automotive alternators that are shown in Figures 16 through 20, and explanation thereof will be omitted.
[0019]
In Figures 1 through 4, a stator 40 is constituted by: a cylindrical stator core 41; and a stator winding 45 that is installed in the stator core 41. The stator 40 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 surfaces of claw-shaped magnetic poles 22 and 23 and an inner surface of the stator core 41.
[0020]
Next, construction of the stator 40 will be explained in detail.
The stator core 41 is prepared by laminating a magnetic steel plate 30 in a similar manner to the conventional stator core 15, and includes^ a cylindrical base portion 43; tooth portions 42 that are each disposed so as to extend toward a central axis from an inner circumferential surface of the base portion 43; and slots 44 that are defined by the base portion 43 and adjacent tooth portions 42. The tooth portions 42 are arrayed at a uniform angular pitch on the inner circumferential surface of the base portion 32. The tooth portions 42 are each formed so as to have a rectangular cross section, and the slots 44 are formed so as to have an approximately trapezoidal shape that tapers radially inward. Each of the tooth portions 42 is formed such that bt/ht = 0.35 (bt = 4 mm; ht = 11.4 mm). Whereas the number of magnetic poles in the rotor 7 is twelve, thirty-six slots 44 are

formed. In other words, the number of slots per phase per pole is one.
[0021]
The stator winding 45 is constituted by a three-phase alternating-current winding in which three winding phase portions 47 that are made by installing conductor wires 46 in wave shapes in every third slot 44 are formed into an alternating-current connection (a wye connection, for example).
Each of the winding phase portions 47 is constituted by a wave winding in which a conductor wire 46 is wound for a predetermined number of turns, and as shown in Figure 5, is formed into a distributed winding that has a wave-shaped pattern that is constituted by twelve slot-housed portions 47a that are arrayed in columns at a pitch of three slots (3P), and linking portions 47b that link a first half of the end portions of adjacent slot-housed portions 47a 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 first and second axial ends. The winding phase portions 47 are installed in the stator core 41 such that the slot-housed portions 47a are housed in every third slot 44. The linking portions 47b that link the end portions of the adjacent slot-housed portions 47a to each other extend circumferentially axially outside the stator core 41 to constitute coil ends. Here, the first half of the linking portions 47b that project out of any given slot 44 extend in a first circumferential direction and enter the next slot 44 in the first circumferential direction, and the second half extend in a second circumferential direction and enter the next slot 44 in the second circumferential direction.
The three winding phase portions 47 are installed in the stator core 41 such that the slots 44 into which they are inserted are offset by one slot (IP) circumferentially from each other and so as to be stacked radially in three layers. The coil ends (i.e., the linking portions 47b) of the three

winding phase portions 47 constitute coil end groups 45f and 45r of the stator winding 45.
[0022]
The conductor wires 46 are conductor wires that are made of a copper wire material that has been coated with an insulator, portions that correspond to the slot-housed portions 47a of the winding phase portions 47 being formed so as to have a rectangular cross section, and portions that correspond to the linking portions 47b being formed so as to have a circular cross section. As shown in Figure 3, ten layers of slot-housed portions 47a are housed with longitudinal axes of their rectangular cross sections aligned circumferentially so as to line up in a single column radially in a slot 44 into which an insulator 51 has been mounted. A wedge 53 is fitted into an opening of the slot 44 such that the slot-housed portions 47a are pressed toward a bottom surface of the slot 44. Thus, the slot-housed portions 47a are placed in close contact with each other, and the slot-housed portion 47a in the outermost layer is in close contact with the bottom surface of the slot 44 with the insulator 51 interposed. In addition, varnish 52 is impregnated into the slot 44 so as to firmly fix the stator core 41 and the stator winding 45. Here in Figure 3, the trapezoidal shape of the slot 44 is exaggerated for convenience, and in reality the difference between the circumferential widths of the slot 44 at a radially-inner end and a radially-outer end is extremely slight and gaps between inner wall surfaces of the slot 44 and the slot-housed portions 47a are very small.
[0023]
As shown in Figure 4, in a stator 40 that is configured in this manner, ventilation channels 100 that are formed by the coil end groups 45f and 45r and the tooth portions 42 of the stator core 41 are arrayed circumferentially. Air discharge apertures lb and 2b are formed on the radial side surfaces of the front bracket 1 and the rear bracket 2 so as to

face the ventilating apertures 100. Moreover, the rest of the configuration is similar to the automotive alternator that is shown in Figures 16 through 20.
[0024]
Next, a method for manufacturing the stator 40 will be explained with reference to Figures 5 through 8.
First, as shown in Figure 5A, a first annular winding unit 48A is prepared by winding one conductor wire 46 that is made of a copper wire material that has a circular cross section that is coated with an insulating coating into a ring shape for five winds, and then a second annular winding unit 48B is prepared by winding the conductor wire 46 into another ring shape for five winds.
Next, as shown in Figure 5B, first and second star-shaped winding sub-units 49A and 49B that have a star-shaped pattern in which end portions of adjacent straight slot-housed portions 49a are alternately linked on an inner circumferential side and an outer circumferential side by linking portions 49b that have an angular C shape are prepared by bending the first and second annular winding units 48A and 48B. In the first and second star-shaped winding sub-units 49A and 49B, twelve bundles of five slot-housed portions 49a are arrayed so as to have a predetermined spacing circumferentially.
A star-shaped winding unit 49 is subsequently prepared by folding the first and second star-shaped winding sub-units 49A and 49B over at a linking portion of the conductor wire 46, and placing the first and second star-shaped winding sub-units 49A and 49B on top of one another such that peak portions and valley portions of the two star-shaped patterns are superposed, as shown in Figure 5C, i.e., such that the linking portions 49b face each other radially.
[0025]

Next, each of the bundles of slot-housed portions 49a of the star-shaped winding unit 49 is set in a press forming machine (not shown). Here, the slot-housed portions 49a in each of the bundles are stacked in single columns in a direction of pressure. All of the bundles of slot-housed portions 49a are pressed simultaneously by a pusher (not shown). The slot-housed portions 49a are thereby plastically deformed from having a circular cross section to having a rectangular cross section. Each of the slot-housed portions 49a has an approximately identical cross-sectional shape.
[0026]
As shown in Figures 6 and 7, a distributed winding unit 50 is prepared by reshaping the star-shaped winding unit 49 into a cylindrical shape. In this distributed winding unit 50, a conductor wire 46 is wound for ten turns into a wave winding. Bundles often slot-housed portions 50a (corresponding to the slot-housed portions 49a that have been plastically deformed so as to have a rectangular cross section) are arrayed at a pitch of three slots circumferentially such that longitudinal directions thereof are parallel to an axial direction. Five of the slot-housed portions 50a in each of the bundles are alternately linked at first and second axial ends by linking portions 50b (corresponding to the linking portions 49b). The remaining five slot-housed portions 50a in each of the bundles are alternately linked in a similar manner at first and second axial ends by linking portions 50b. Moreover, the linking portions 50b that link each set of five slot-housed portions 47a face each other axially.
[0027]
Next, the linking portions 50b at the first axial end of the distributed winding unit 50 are bent radially inward. As shown in Figure 8, the distributed winding unit 50 is then mounted to the stator core 41 from an axial direction. Here, portions of the linking portions 50b that

have been bent radially inward that are in a vicinity of the slot-housed portions 50a are moved axially through opening portions of the slots 44, leading the slot-housed portions 50a into the slots 44. After the slot-housed portions 50a have been led completely into the slots 44, the linking portions 50b that that have been bent radially inward are restored so as to extend axially, completing the mounting of a first distributed winding unit 50 into the stator core 41.
A second distributed winding unit 50 is similarly mounted to the stator core 41 such that the slots 44 into which it is inserted are offset by one slot. A third distributed winding unit 50 is similarly mounted to the stator core 41, obtaining the stator 40 that is shown in Figure 2. Here, the distributed winding units 50 that are mounted to the stator core 41 constitute the respective winding phase portions 47 of the stator winding 45. The slot-housed portions 50a and the linking portions 50b of the distributed winding units 50 correspond to the slot-housed portions 47a and the linking portions 47b of the winding phase portions 47.
[0028]
According to Embodiment 1, because the ratio (bt/ht) between the width bt and the radial length ht of the tooth portions 42 of the stator core 41 is set to 0.35, narrower ventilation channels 100 are formed than in the conventional stator 8 in which bt/ht was equal to 0.42. Thus, because the cooling airflows that are generated by the cooling fans 5 pass through the narrower ventilation channels 100, the velocity of the cooling airflows is higher and heat generated in the stator winding 45 is radiated to the cooling airflows efficiently, suppressing temperature increases in the stator 40.
Because temperature increases in the stator 40 are suppressed, improvements in output can be achieved. In addition, since heat degradation that results from softening of the varnish 52 is suppressed

even under the worst operating conditions, damage to the insulating coating on the conductor wires 46 that results from abrasion between the conductor wires 46 of the stator winding 45 and the stator core 41 is also prevented, improving electrical insulation.
[0029]
Because the cooling fans 5 are fixed to the axial end surfaces of the rotor 7, the cooling airflows are conveyed to the ventilation channels 100 forcibly by the cooling fans 5, increasing the cooling of the coil end groups 45f and 45r.
Because the air discharge apertures lb and 2b are disposed facing the ventilation channels 100, the cooling airflows that flow through the ventilation channels 100 are discharged from the air discharge apertures lb and 2b promptly. Thus, ventilation resistance is reduced, increasing the cooling of the coil end groups 45f and 45r and reducing wind noise.
[0030]
Because the stator core 41 is fitted into the front bracket 1 and the rear bracket 2, heat generated in the stator winding 45 is transferred to the front and rear brackets 1 and 2 through the stator core 41. The heat that has been transferred to the front and rear brackets 1 and 2 is radiated to the cooling airflows that flow through the air discharge apertures lb and 2b. Thus, temperature reduction in the stator 40 is accelerated.
[0031]
Because each of the winding phase portions 47 that constitute the stator winding 45 is constituted by a distributed winding, the linking portions 47b (the coil ends) of the winding phase portions 47 that project out of the slots 44 are distributed half each in first and second circumferential directions. Thus, because the bundles of linking portions 47b are slenderer, bending stresses that act on the linking portions 47b as a result of the bundles of the linking portions 47b interfering with each

other when stacked radially are reduced. Thus, even if such bending stresses are concentrated at boundary portions between the slot-housed portions 47a and the coil end portions 47b, insulating coatings at the boundary portions are less likely to be damaged, suppressing the occurrence of incidents of short-circuiting among the conductor wires 46. Because radial overlap between the bundles of linking portions 47b is dispersed circumferentially, irregularities on inner wall surfaces of the ventilation channels 100 are reduced. Wind noise arising as a result of pressure fluctuations between the coil end groups 45f and 45r and the rotor 7 or between the coil end groups 45f and 45r and the fans 5 is thereby reduced.
[0032]
The linking portions 47b (50b) may rub against each other when the distributed winding units 50 are being mounted to the stator core 41, when the linking portions 50b of the distributed winding units 50 that have been mounted to the stator core 41 are reshaped, and when vibrations from a vehicle act on the automotive alternator. Here, because the linking portions 47b (50b) are formed so as to have a circular cross section, the occurrence of damage to insulating coatings that results from the linking portions 47b (50b) rubbing against each other is suppressed, improving electrical insulation.
[0033]
Because the slot-housed portions 47a are housed inside the slots 44 with longitudinal axes of their rectangular cross sections aligned circumferentially so as to line up in single columns radially, improvements in space factor can be achieved, enabling an alternator that has high output to be achieved. Because the slot-housed portions 47a that are housed inside the slots 44 are placed in close contact with each other, space factor is further increased.

Inner circumferential linking portions 47b are more likely to be cooled by the fans 5, and outer circumferential linking portions 47b are less likely to be cooled by the fans 5. However, because the slot-housed portions 47a are placed in close contact with each other, heat transfer occurs easily between the slot-housed portions 47a, making the temperature of the slot-housed portions 47a uniform. Thus, excessive local temperature increases are suppressed in the stator winding 45.
Because the slot-housed portions 47a in the outermost layers are placed in close contact with the bottom surfaces of the slots 44 with the insulators 51 interposed, heat from the stator winding 45 is transferred to the stator core 41 efficiently, suppressing excessive temperature increases in the stator winding 45.
[0034]
The relationship between the ratio (bt/ht) between the width bt and the radial length ht of the stator core 41 and stator temperature increase will now be investigated. Here, increases in saturation temperature from an experimental ambient temperature (20°C) when automotive alternators that were mounted with stators in which bt/ht was changed were made to generate power under full load and the saturation temperature of the stators was measured when output was stable are shown in Figure 9. Moreover, in Figure 9, bt/ht is shown on the horizontal axis, and temperature increase (°C) from the experimental ambient temperature (20°C) of the stator is shown on the vertical axis. Furthermore, saturation temperatures for each stator were measured while running at 3,000, 3,500, 4,000, 4,500, and 5,000 rpm, and the maximum value was taken as the saturation temperature for the stator.
[0035]
From Figure 9, it can be seen that stator temperature increase adopts a curve that has a point of inflection at bt/ht = 0.27. Thus, in a

region where 0.15 It can be inferred from this that when bt/ht is less than 0.27, the ventilation channels 100 become narrow, the velocity of the cooling airflows that pass through the ventilation channels 100 is high, and heat transfer to the cooling airflows from inner wall surfaces of coil end groups that constitute the ventilation channels 100 is facilitated, but when bt/ht is less than 0.15, the ventilation channels 100 become too narrow, and the quantity of cooling airflow that passes through the ventilation channels 100 becomes extremely small, giving rise to decreases in the velocity of the cooling airflows and making cooling poor. It can also be inferred that when bt/ht is greater than 0.27, ventilation resistance in the ventilation channels 100 decreases sharply and the quantity of cooling airflow increases, the velocity of the cooling airflows is effectively higher, and heat transfer to the cooling airflows from inner wall surfaces of coil end groups that constitute the ventilation channels 100 is facilitated, but when bt/ht is greater than 0.4, the ventilating cross-sectional area of the ventilation channels 100 becomes too wide, giving rise to decreases in the velocity of the cooling airflows and making cooling poor.
[0036]
Thus, since the softening temperature of the varnish 52 is 230 degrees Celsius, when consideration is given to decreases in output that result from decreases in field current due to ambient temperature increases,

the temperature of the stator will be prevented from exceeding the softening temperature of the varnish 52 even under the worst operating conditions if the temperature increase at an ambient temperature of 90 degrees Celsius is suppressed to less than or equal to 140 degrees Celsius. A temperature increase of 140 degrees Celsius at an ambient temperature of 90 degrees Celsius corresponds to a temperature increase of 170 degrees Celsius at an ambient temperature of 20 degrees Celsius. Consequently, when consideration is given to softening of the varnish 52, it is desirable for bt/ht to be set so as to be greater than 0.15 and less than 0.4, as can be seen from Figure 9. An automotive alternator can thereby be achieved in which resistance to heat degradation is improved and deterioration of electrical insulation that results from loosening of the bonding between the stator core 41 and the stator winding 45 is suppressed.
In addition, it can be seen from Figure 9 that stator temperature increase stabilizes between 166.3 degrees Celsius and 165 degrees Celsius when bt/ht is greater than or equal to 0.22 and less than or equal to 0.32. Thus, a high-output automotive alternator can be achieved by setting bt/ht so as to be greater than or equal to 0.22 and less than or equal to 0.32, because the temperature of the stator can be kept low even more stably.
[0037]
Moreover, in Embodiment 1 above, the linking portions are formed so as to have a rectangular cross section, but the cross-sectional shape of the linking portions need only be flat, and may also be a cross-sectional shape in which two ends of facing parallel long sides are linked by arcs, for example.
In Embodiment 1 above, first and second annular winding units 48A and 48B are prepared from one conductor wire 46, but the first and second annular winding units 48A and 48B may also be prepared using a separate conductor wire for each.

In Embodiment 1 above, insulators 51 are mounted into the slots 44, but the insulators 51 may also be omitted.
[0038] Embodiment 2
Figure 10 is a perspective of a stator of an automotive alternator according to Embodiment 2 of the present invention, Figure 11 is a partial side elevation of the stator of the automotive alternator according to Embodiment 2 of the present invention, Figure 12 is a partial cross section that shows a slot-housed state of a stator winding in the stator of the automotive alternator according to Embodiment 2 of the present invention, Figure 13 is a perspective of a single winding phase portion in the stator of the automotive alternator according to Embodiment 2 of the present invention, and Figure 14 is an enlargement of part of the single winding phase portion in the stator of the automotive alternator according to Embodiment 2 of the present invention.
In Figures 10 through 14, a stator 40A is constituted by- a stator core 41A; and a stator winding 45A that is installed in the stator core 41A. The stator core 41Ais prepared in a similar manner to the stator core 41 in Embodiment 1 above, and tooth portions 42A that are disposed so as to extend from a base portion 43A are formed such that bt/ht = 0.25 (bt - 2.5 mm; ht = 10.0 mm). Seventy-two slots 44A are formed on the stator core 41A. Here, because the number of magnetic poles in the rotor 7 is twelve, the number of slots per phase per pole is two.
[0039]
The stator winding 45A is constituted by two three-phase alternating-current windings in each of which three out of six winding phase portions 47A that are made by installing conductor wires 46A in wave shapes in every sixth slot 44 are formed into an alternating-current connection (a wye connection, for example).

Each of the winding phase portions 47A is constituted by a wave winding in which a conductor wire 46A 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 47a that are arrayed in columns at a pitch of six slots, and linking portions 47b that link a first half of the end portions of adjacent slot-housed portions 47a 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 first and second axial ends.
[0040]
The winding phase portions 47A are installed in the stator core 41A such that the slot-housed portions 47a are housed in respective slots 44A that are arrayed at a pitch of six slots.
The six winding phase portions 47A are installed in the stator core 41A so as to be offset by one slot (IP) circumferentially from each other and so as to be stacked radially in six layers. The coil ends (i.e., the linking portions 47b) of the six winding phase portions 47A constitute coil end groups 45f and 45r of the stator winding 45A.
[0041]
The conductor wires 46A are conductor wires that are made of a copper wire material that has been coated with an insulator, portions that correspond to the slot-housed portions 47a of the winding phase portions 47A being formed so as to have a flat cross section, and portions that correspond to the linking portions 47b being formed so as to have a circular cross section. In addition, as shown in Figure 14, slot opening passing portions 47c are configured by deforming boundary portions between the slot-housed portions 47a and the linking portions 47b of the conductor wires 46A so as to have flat cross sections. The slot opening passing portions 47c are formed so as to have a radial thickness equivalent to that

of the slot-housed portions 47a and a circumferential length that is shorter than the opening portions of the slots 44.
[0042]
As shown in Figure 12, the slot-housed portions 47a are housed in six layers with longitudinal axes of their flat cross sections aligned circumferentially so as to line up in a single column radially in a slot 44A into which an insulator 51 has been mounted. A wedge 53 is fitted into an opening of the slot 44A such that the slot-housed portions 47a are pressed toward a bottom surface of the slot 44A. Thus, the slot-housed portions 47a are placed in close contact with each other, and the slot-housed portion 47a in the outermost layer is in close contact with the bottom surface of the slot 44A with the insulator 51 interposed. In addition, varnish 52 is impregnated into the slot 44A so as to firmly fix the stator core 41A and the stator winding 45A.
[0043]
In a stator 40A that is configured in this manner, ventilation channels lOOAthat are formed by coil end groups 45f and 45r and the tooth portions 42A of the stator core 41A are also arrayed circumferentially. Moreover, the rest of this embodiment is configured in a similar manner to Embodiment 1 above.
[0044]
In Embodiment 2, because the tooth portions 42A of the stator core 41A are formed such that bt/ht = 0.25, heat radiation from the coil end groups 45f and 45r is increased compared to Embodiment 1 above which is formed such that bt/ht = 0.35, enabling temperature increases in the stator 40Ato be suppressed.
Because the slots 44A are formed at a ratio of two slots per phase per pole, the number of ventilation channels 100A that are formed between the coil end groups 45f and 45r and the end surfaces of the stator core 41A

is twice that of Embodiment 1 above, further suppressing temperature increases in the stator 40A and reducing wind noise.
[0045]
In Embodiment 2, because the slot opening passing portions 47c are formed on the winding phase portions 47A, the slot opening passing portions 47c at the boundary portion between the slot-housed portions 47a and the linking portions 47b move axially through the opening portions of the slots 44 as the distributed winding units are being mounted from an axial direction relative to the stator core 41A, leading the slot-housed portions 47a into the slots 44A. Thus, contact between the conductor wires 46A and the stator core 41A can be avoided as the winding phase portions 47A are being mounted to the stator core 41A, suppressing the occurrence of damage to the electrically-insulating coating.
[0046] Embodiment 3
In Embodiment 3, as shown in Figure 15, entire axial lengths of blades 5a of cooling fans 5 approximately overlap with coil end groups 45f and 45r radially. Moreover, the rest of this embodiment is configured in a similar manner to Embodiment 2 above.
According to Embodiment 3, because the entire axial lengths of the blades 5a of the cooling fans 5 approximately overlap with the coil end groups 45f and 45r radially, cooling airflows that are generated by the cooling fans 5 are reliably supplied to the coil end groups 45f and 45r, increasing the cooling of the coil end groups 45f and 45r. In addition, because a discharge side of the cooling fans 5 is shielded by the coil end groups 45f and 45r, emission of noise is blocked, reducing wind noise.
[0047]
Moreover, in each of the above embodiments, stator cores in which

the number of slots per phase per pole is one or two have been explained, but similar effects can also be achieved if the present invention is applied to stator cores in which the number of slots per phase per pole is three or more.
In each of the above embodiments, application to automotive alternators in which a field winding 13 is wound onto pole cores 20 and 21 so as to be covered by claw-shaped magnetic poles 22 and 23 and rotates together with the claw-shaped magnetic poles and a field current is supplied to the field winding by means of brushes 10 has been explained, but similar effects are also exhibited when the present invention is applied to brushless automotive alternators in which a field winding is fixed to a bracket and a rotating magnetic field is supplied to the stator across an air gap.
In each of the above embodiments, a stator core is prepared by winding a long magnetic steel plate into a helical shape, but the method for manufacturing the stator core is not limited to that method, and stator cores may also be prepared, for example, by preparing a rectangular parallelepiped laminated core by laminating a predetermined number of strip-shaped magnetic steel plates, bending that laminated core into an annular shape, and abutting and welding end surfaces of the bent laminated core to each other.
In each of the above embodiments, conductor wires in which slot-housed portions have a rectangular cross section and linking portions have a circular cross section are used, but it goes without saying that conductor wires that have a rectangular cross section overall may also be used.



WHAT IS CLAIMED IS:
1. An automotive alternator comprising:
a shaft that is rotatably supported by a case;
a rotor that is fixed to said shaft, said rotor comprising:
a field winding that generates magnetic flux on passage of electric current; and
a plurality of claw-shaped magnetic poles that are arrayed circumferentially around said field winding so as to be magnetized by said magnetic flux that is generated by said field winding! a stator that has:
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! and a cooling fan that is fixed to an axial end surface of said rotor, characterized in that:
said stator core is configured by laminating a magnetic steel plate, said stator comprising:
a cylindrical base portion!
a plurality of tooth portions that are disposed so as to extend toward a central axis from said base portion! and
said plurality of said slots that are defined by said base portion and adjacent tooth portions! ventilation channels through which cooling airflows pass from radially inside due to rotation of said rotor are formed by coil end groups of said stator winding and said tooth portions of said stator core!
said tooth portions are formed such that a radial length ht and a width bt satisfy an expression 0.15
said stator winding has a plurality of winding portions that are installed in respective slot groups that are constituted by slots of said stator core that are separated by a predetermined number of slots!
each of said winding portions is configured by winding a conductor wire in a distributed winding in said slot groups so as to extend outward from two ends of said slots, be distributed in first and second circumferential directions, and enter each of said slots that are separated by said predetermined number of slots in said first and second circumferential directions;
said conductor wire has slot-housed portions that are housed in said slots and that are formed so as to have flat cross sections; and
said slot-housed portions are housed inside said slots in a plurality of layers with longitudinal axes of said flat cross sections aligned circumferentially so as to be arrayed in single columns radially.
2. An automotive alternator according to Claim 1, wherein said
slot-housed portions that are arrayed in single columns radially contact each other inside said slots, and said slot-housed portions in an outermost layer contact a bottom surface of said slots.


Documents:

926-che-2007 amended claims 08-03-2011.pdf

926-che-2007 amended claims 11-02-2011.pdf

926-CHE-2007 CORRESPONDENCE OTHERS 08-03-2011.pdf

926-che-2007 correspondence others 11-02-2011.pdf

926-CHE-2007 CORRESPONDENCE OTHERS 18-02-2011.pdf

926-che-2007 form-3 08-03-2011.pdf

926-CHE-2007 FORM-5 08-03-2011.pdf

926-CHE-2007 AMENDED PAGES OF SPECIFICATION 10-08-2010.pdf

926-CHE-2007 CORRESPONDENCE OTHERS 06-09-2010.pdf

926-CHE-2007 EXAMINATION REPORT REPLY RECEIVED 10-08-2010.pdf

926-CHE-2007 POWER OF ATTORNEY 10-08-2010.pdf

926-che-2007-abstract.pdf

926-che-2007-claims.pdf

926-che-2007-correspondnece-others.pdf

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

926-che-2007-drawings.pdf

926-che-2007-form 1.pdf

926-che-2007-form 18.pdf

926-che-2007-form 3.pdf


Patent Number 246846
Indian Patent Application Number 926/CHE/2007
PG Journal Number 12/2011
Publication Date 25-Mar-2011
Grant Date 17-Mar-2011
Date of Filing 01-May-2007
Name of Patentee MITSUBISHI ELECTRIC CORPORATION
Applicant Address 7-3, MARUNOUCHI 2-CHOME CHIYODA-KU TOKYO 100-8310
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
PCT International Classification Number H02K 3/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA