TECHNICAL FIELD
The present disclosure, in general, relates to an automotive alternator driven by an internal combustion engine. The present disclosure particularly relates to an automotive alternator that can realize high output, high efficiency and improved cooling.
BACKGROUND
Conventional alternators are used in all types of motor vehicles, such as passenger cars and trucks. An alternator is an electromechanical device that converts mechanical energy into alternating current (AC) electrical energy. Automotive alternators are mechanically driven using a drive belt wrapped on a pulley connected to a crankshaft of a vehicle's internal combustion engine. The belt drives the pulley that rotate an internal rotor assembly of the alternator to generate alternating current (AC) electrical power from stator winding of the alternator. This AC power is rectified to a direct current (DC) supply coimected to a storage battery of the vehicle.
There has been a dramatic increase in the number of electrical on-board systems and accessories in contemporary motor vehicles. Present day requirements have demand for efficient motor vehicle design, cost, and performance demands, which have in turn placed more emphasis on having more efficient alternator designs. Compounding these design challenges is the fact that with electrical system demands for vehicles varying widely, the need to increase the output of an alternator at lower speeds has become critical. Moreover, there is also a need for an improved cooling mechanism to control temperature rise of the rotor and stator winding of an alternator, especially when a high electrical output is being provided by the alternator. This is usually achieved by

increasing the rate of cooling airflow passing through the rotor coil; however, such a mechanism directly leads to an increase in operating noise.
In addition to above said challenges, there is a growing need to enhance power density of alternators to meet the under hood packaging requirements.
Fig. 1 illustrates a sectional view of a conventional automotive alternator 100. The rotor 105 includes an exciting winding and a pair of pole cores, which are disposed circumferentially on the shaft 110. The front-end bracket 115 and a rear-end bracket 120 120 are made from cast aluminium and a stator 125 is mounted between the front-end and the rear-end brackets. The front-end bracket 115 can be a drive end bracket (hereinafter, referred to as DE frame), and the rear-end bracket 120 can be a slip ring end bracket (hereinafter, referred to as SRE frame). Further, the stator 125 includes a core, made of thin stacked laminations to form a hollow cylinder in which the coils of insulated round conducting wires are inserted into slots of the stator core.
A pulley 130 is assembled to the drive end of shaft 110 such that a rotational torque from the vehicle engine can be transmitted to the shaft 110 by means of a belt. Slip rings for supplying electric current to the rotor 105 are assembled to the shaft 110 on the rear end. A rectifier 135 is connected to the stator 125, which converts alternating current (AC) generated in the stator into direct current (DC). Centrifiigal fans 140A and 140B are provided on both faces of the rotor 105 for cooling sub-assemblies of the alternator 100. A rotational torque from the engine is transmitted through the belt and the pulley 130 to the shaft 110, thus rotating the rotor 105. When the rotor 105 rotates, a rotating magnetic field is applied to the stator, thus generating an alternating current (AC) in the stator

winding. The rectifier 135 rectifies the AC output produced in the stator to DC and a regulator controls the output voltage to the required level, and the battery is charged.
During the alternator operation, the sub-assemblies are heated up due to losses in the sub-assemblies such as, copper loss in stator & field windings, rectification loss in rectifier, switching loss in regulator and frictional losses in front & rear bearings. In order to provide cooling, the DE and SRE frames are typically ventilated to allow airflow through the machine. The front fan 140A draws air currents 170A & 170B axially through the openings 145A & 145B in the DE frame 115 and exits out radially through openings 155A & 155B in DE frame 115. The rear fan 140B draws air currents 165A & 165B axially through the openings 150A & 150B in the SRE assembly and exits out radially through openings 160A & 160B in SRE frame 120.
The conventional alternator with the above construction has the disadvantages such as lower output at idling speed of engine, lower efficiency, and lower power density. Another disadvantage of conventional alternator includes welding of metallic internal fans on to rotor claw faces, which requires periodic electrode maintenance and controlled plating finish of the fans.
Hence, there exists a need for an automotive alternator that is compact in size, higher in electrical output and lower in operating noise.
SUMMARY
The present subject matter has been devised in view of the foregoing and has an object to provide an alternator for motor vehicles that is capable of providing high electrical output and increased cooling of underlying parts such as stator coil, rotor

winding, and rectifier. In addition, the alternator described herein is compact and has low operating noise.
In order to achieve the above object, according to one aspect of the subject matter, there is provided an alternator including a rotor supported by a front-end bracket and a rear-end bracket. In one embodiment, the rotor has a pair of Lundell-type pole cores disposed inside the brackets, and a stator supported by the brackets, the stator being disposed so as to cover an outer circumference of the rotor. The stator includes a cylindrical stator core in which a plurality of slots having grooves lying in an axial direction are disposed circumferentially so as to open onto an inner circumferential side. The stator further includes a stator coil installed in the stator core so as to include a predetermined winding construction.
The proposed ahemator housing includes air intake apertures including a plurality of air intake apertures being disposed in axial and radial end surfaces of front-end bracket and a plurality of air intake apertures being disposed in axial end surfaces of rear-end bracket and a plurality of stator core apertures disposed on the circumferential side of the stator core to facilitate air passage. The proposed alternator further includes a plurality of air discharge apertures being disposed in radial side surface of said rear-end bracket, and a fan assembly disposed at rear axial end of the rotor.
The fan assembly includes a plurality of blades provided on each surface of a disc. The disc is provided on a sleeve portion of the fan assembly such that the disc is perpendicular to the axis of the sleeve portion. This arrangement of fan helps to simplify the manufacturing process of rotor assembly since the manufacturing process of welding two fans onto either side of claw faces is eliminated and a simple moulded fan is driven into the rotor shaft. The cooling of the alternator could be further improved by providing

opening in stator core at predetermined intervals extending from inner circumferential surface to outer circumferential surface. The airflow with this arrangement could be fine tuned by provision of a baffle arrangement between fan and rear-end bracket.
An advantage of the subject matter disclosed above is to provide a superior cooling arrangement of the stator winding. In addition, slot fill factor of stator winding could be enhanced by use of wires with rectangular cross section instead of circular cross section which helps to bring down the stator winding resistance thereby reducing the copper loss of ahemator leading to higher alternator efficiency.
These and other features, aspects, and advantages of the present subject matter will become better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features, aspects, and advantages of the subject matter will become better understood with regard to the following description, appended claims, and accompanying drawings where:
Fig.l illustrates a sectional view of a conventional automotive alternator. Fig.2 illustrates an exemplary sectional view of an automotive alternator according to first embodiment of the present subject matter.
Fig. 3 illustrates an exemplary view of a fan assembly included in the alternator.

Fig.4 illustrates an exemplary sectional view of an alternator according to second embodiment of the present subject matter.
Fig.5 illustrates an exemplary view of a stator assembly according to the present subject matter.
Fig.6 illustrates an exemplary view of a stator core assembly of the stator assembly according to the present subject matter.
DESCRIPTION
An alternator for automobiles with improved cooling system, higher output, and reduced noise is described. The alternator includes a Lxmdell-type rotor with N and S poles formed alternately in a circumferential direction, a stator including a stator core and a poly-phase stator winding associated with the stator core and front-end and rear-end brackets supporting the rotor and the stator.
The stator core comprises laminated cores formed with a plurality of slots extending across laminated plates in the axial direction of the stator core. The stator design employs wire conductors laced into the stator core winding slots. In one embodiment, the conducting wires can be round cross-sectional conducting wires. In another embodiment, the conducting wires can be rectangular in cross-section.
In yet another embodiment, round conducting wire can be formed to rectangular section for the slot portion. The conducting wires are formed as either segmented or continuous conducting wires that allows larger cross sectional areas to be provided for the conductors in the slot. This lowers the resistance of the conductors, thereby reducing copper losses. At the same time, the number of poles can be suitably increased, which

helps to reduce stator winding overhang leading to reduced winding resistance and reduced leakage inductance.
The present invention includes a fan, which has blades on both faces, internally mounted, for cooling an alternator. The fan draws a plurality of separate airflow currents through air intake apertures at the front-end and rear-end brackets into the housing and expels the air currents radially through the air discharge apertures at the rear-end bracket. To minimize the temperature rise of the stator assembly further, the aforementioned stator core design is employed. In this design, the stator core will have multiple stator core apertures disposed on the circumferential side of the stator core to facilitate air passage.
Fig.2 illustrates an exemplary sectional view of an automotive alternator 200 according to first embodiment of the present subject matter. The alternator 200 includes the rotor 105, and the stator 125 that acts as an armature. The rotor 105 includes a winding and a pair of claw shaped pole cores that are disposed circumferentially about the shaft 110. The stator 125 includes a stator core and a stator coil having a predetermined winding construction. The stator core includes a number of slots having grooves lying in an axial direction and that are disposed on circumferential side of the stator core. The grooves receive a plurality of conducting wires that are either circular or rectangular in cross-section. In yet another embodiment, the conductors can be round formed to rectangular section for the slot portion. The conducting wires are segmented and winding is formed by joining appropriate conductor ends through relevant joining process such as welding or brazing or soldering. In another implementation, the conducting wires are continuously wound around the stator core.

A pair of frames such as DE 115 and SRE 120 frames (also referred to as the front-end and the rear-end brackets, respectively), are provided for supporting both the rotor 105 and the stator 125. Both frames 115 and 120 are typically cast from aluminum and support the stator 125 and the rotor 105 as well as other components that make up the automotive alternator 200. The automobile alternator 200 further includes air intake apertures 155A and 155B disposed in the radial side surfaces of the DE frame 115 and air intake apertures 150A and 150B disposed in axial end surfaces of the SRE frame 120. In addition, the alternator 200 includes air discharge apertures 160A and 160B disposed in radial side surfaces of the SRE frame 120. Furthermore, the alternator 200 includes a fan assembly 205 (as illustrated in Fig.3) disposed at a rear axial end of the rotor 105. The fan assembly 205 includes a plurality of blades provided on each surface of a disc. The disc is provided on a sleeve portion of the fan assembly 205 such that the disc is perpendicular to the axis of the sleeve portion.
The alternator 200 further comprises a pulley 130 fastened to a front end of the alternator shaft 110 and a rectifier 135 whose output is connected to a battery (not shown). Generally, the alternator 200 is driven by a belt mounted on the pulley 130 that is connected to the engine shaft of the vehicle. The rectifier 135 then converts the generated alternating current (AC) into direct current (DC).
Further, in order to improve overall efficiency of the alternator 200, the temperature rise of the inner sub-assemblies of the alternator 200 are kept at a minimum level by cooling its sub-assemblies such as the stator 125, the rotor 105, and the rectifier 135. Cooling is provided by means of the rotating fan assembly 205 that draws air currents into the alternator 200 and expels heat from the inner sub-assemblies through

circulation of air, thereby maintaining the temperature at a minimum level. In one embodiment, a baffle arrangement can be provided around the fan assembly to optimize airflow. A first pair of air currents 165A and 165B enters the SRE frame 120 through a number of air-intake apertures, such as 150A and 150B, in an axial direction into the alternator 200. The first pair of currents 165A and 165B is then redirected to a radial flow by the blades and the disc of the fan assembly 205 and finally exit the SRE frame 120 through the air discharge apertures 160A and 160B.
A second pair of air currents 170A and 170B is drawn through the air intake apertures 155A and 155B in the DE frame 115. As the air currents 170A and 170B encounter the blades and the disc of the fan assembly 205, they are redirected to a radial flow and finally exit the SRE frame 120 through discharge apertures 160A and 160B. The disc minimizes any substantial mixing of the air currents 165A, 165B, and 170A, 170B before they exit the housing, thereby increasing the cooling efficiency of the fan assembly 205.
Fig.3 illustrates an exemplary view of a fan assembly 205 included in the alternator 200. The fan assembly 205 is generally a disc-shaped body 305 having opposed first and second faces. Each face of the disc 305 includes a plurality of blades 310. The fan assembly 205 includes a cylindrical sleeve portion 315 with a central opening for receiving the alternator shaft 110. The sleeve portion can be held to the shaft 110 by any suitable fastening means. In one implementation, the sleeve portion 315 can be fastened to the shaft 110 by press fitting. The disc 305 is provided on the sleeve portion 315 and is oriented in a way such that the plane of the disc 305 is perpendicular to the axis of the sleeve portion 315.

Fig.4 illustrates an exemplary sectional view of an alternator 400 according to second embodiment of the present subject matter. The alternator 400 resembles the construction and working of the alternator 200 as described with respect to Fig.2. According to second embodiment of the present subject matter, the alternator 400 includes the stator 125 having a stator core and a plurality of stator core apertures 410A & 410B disposed on the circumferential side of the stator core to facilitate air passage.
When the shaft 110 and the attached fan assembly 205 are rotated, a first pair of air currents 165A and 165B enters the SRE frame 120 through one or more air intake apertures, such as 150A & 150B, in an axial direction into the alternator 400. The first pair of currents 165 A and 165B is then redirected to a radial flow by the blades 310 of the fan assembly 205 and finally exits the SRE frame 120 through air discharge apertures 160A and 160B.
A second pair of air currents 170A and 170B is drawn through the air intake apertures 155A and 155B of the DE frame 115. In this embodiment, a third pair of air currents 405A and 405B is drawn radially through the stator core apertures 410A and 410B. As the air currents 405A, 405B, and 170A & 170B are mixed and encounter the blades 310, these air currents are redirected to a radial flow, and finally exit the SRE frame 120 through air discharge apertures 160A and 160B.
Fig. 5 illustrates an exemplary view of a stator assembly 125 according to the present subject matter. The stator assembly 125, according to embodiments described with respect to Fig. 4 of the alternator 400, includes a stator core 505 and a stator coil 510. The stator coil 510 includes a predetermined winding construction. The stator core 505 includes a number of slots having grooves lying in an axial direction that are

uisposea on circumterential side of the stator core 505. The grooves receive a plurality of conducting wires 515 that are either circular or rectangular in cross-section. The stator coil 510 can be formed by conducting wires 515 that are either segmented or continuously wound around the inner circumferential side of the stator core 505.
The stator core 505 includes a plurality of stator core apertures 410, such as stator core apertures 410A and 410B, on the circumferential side of the stator core 505 to facilitate the flow of air through the stator core 505. The construction of the stator core 505 with multiple stator core apertures 410 is well described in Fig. 6.
Fig.6 illustrates an exemplary view of the stator core assembly 505 according to the present subject matter. The stator core assembly 505 as shown in Fig. 6 includes a plurality of stator core apertures 410 on the circumferential side of the stator core 505 to facilitate the flow of air through the stator core 505. The stator core 505 includes plurality of stack of punchings 605 arranged in arrays of annular layer. The annular layer of 605 is held between core stacks 610A & 610B to form the stator core 505. This kind of arrangement facilitates gaps 605 between adjacent stacks there by facilitating air to pass through the stator core apertures 410 for cooling of stator. In another embodiment, it is also possible to repeat the annular layers at multiple axial positions of stator to optimize the cooling performance.
Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein.

Claims
I/We claim:
1. An automotive alternator 200 comprising:
a rotor 105 rotatably supported by a front-end bracket 115 and a rear-end
bracket 120, said rotor 105 having pole cores
a stator 125 supported by said brackets 115 and 120, said stator 125 being
disposed so as to cover an outer circumference of said rotor 105, said
stator 125 comprising,
a cylindrical stator core 505 in which a plurality of slots having grooves lying in an axial direction are disposed circumferentially so as to open onto an inner circumferential side; and a stator coil 510 installed in said stator core 505 so as to form a predetermined winding construction;
a pulley 130 assembled to a front end of a shaft 110;
a rectifier 135 disposed at a rear end of said rotor 105;
air intake apertures including a plurality of air intake apertures 155A and
155B being disposed in axial end surfaces of front-end bracket 115 and a
plurality of air intake apertures 150A and 150B being disposed in radial
end surfaces of rear-end bracket 120;
a plurality of air discharge apertures 160A and 160B being disposed in
radial side surface of said rear-end bracket 120; and
a fan assembly 205 disposed at a rear axial end of said rotor 105;
characterized in that

said fan assembly 205 including a plurality of blades 310 provided on each surface of a disc 305, wherein said disc 305 is provided on a sleeve portion of said fan assembly 205 such that said disc 305 is perpendicular to the axis of said sleeve portion, and wherein
said air intake apertures 150A and 150B at said rear-end bracket 120 allow a first pair of air currents 165A and 165B to be drawn in and said rear-end air discharge apertures 160A and 160B expel the air currents; wherein said air intake apertures 155A and 155B at said front-end bracket 115 allow a second pair of air currents 170A and 170B to be drawn in and said rear-end air discharge apertures 160A and 160B expel the air currents.
2. The alternator according to claim 1, wherein said predetermined winding includes conducting wires 515 having roimd cross-section or rectangular cross-section.
3. The alternator according to claim 1, wherein said predetermined winding is formed of continuous or segmented conducting wires 515.
4. An automotive alternator 400 comprising:
a rotor 105 rotatably supported by a front-end bracket 115 and a rear-end
bracket 120 , said rotor 105 having pole cores;
a stator 125 supported by said brackets 115 and 120, said stator 125 being
disposed so as to cover an outer circumference of said rotor 105, said
stator 125 comprising,
a cylindrical stator core 505 in which a plurality of slots having grooves lying in an axial direction are disposed circumferentially so as to open onto an inner circumferential side; and

a stator coil 510 installed in said stator core 505 so as to form a
predetermined winding construction; a pulley 130 assembled to a front end of a shaft 110; a rectifier 135 disposed at a rear end of said rotor 105; air intake apertures including a plurality of air intake apertures 155A and 155B being disposed in axial end surfaces of front-end bracket 115 and a plurality of air intake apertures 150A and 150B being disposed in radial end surfaces of rear-end bracket 120;
a plurality of air discharge apertures 160A and 160B being disposed in radial side surface of said rear-end bracket 120; and a fan assembly 205 disposed at a rear axial end of said rotor 105; characterized in that
said fan assembly 205 including a plurality of blades 310 provided on each surface of a disc 305, wherein said disc 305 is provided on a sleeve portion of said fan assembly 205 such that said disc 305 is perpendicular to the axis of said sleeve portion; and
a plurality of stator core apertures 410A and 410B are disposed in said stator core 505 at predetermined intervals extending from inner circumferential surface to outer circumferential surface of said stator core 505; wherein
said air intake apertures 150A and 150B at said rear-end bracket 120 allow a first pair of air currents 165A and 165B to be drawn in and said rear-end air discharge apertures 160A and 160B expel the air currents; wherein said air intake apertures 155A and 155B at said front-end bracket

115 allow a second pair of air currents 170A and 170B to be drawn in and said rear-end air discharge apertures 160A and 160B expel the air currents; wherein said stator core apertures 410A and 41 OB allow a third pair of air currents 405A and 405B to be drawn in and said rear-end air discharge apertures 160A and 160B expel the air currents to cool said predetermined winding.
5. The alternator according to claim 4, wherein said predetermined winding includes
conducting wires 515 having round cross-section or rectangular cross-section.
6. The alternator according to claim 4, wherein said predetermined winding is
formed of continuous or segmented conducting wires 515.