FRONT FAN RETENTION IN DUAL INTERNAL FAN ALTERNATOR
An alternator has a pole segment with a collar, an axially outward surface, and at least one key extending radially outward from the collar along the surface. A fan has a keying slot extending radially outward from a center ring, and a fan body including protrusions. The fan is mounted to the segment whereby the collar fits inside the ring and the key fits inside the keying slot, and the fan is welded to the segment at the protrusions. A method includes securing a fan to a pole segment by mating a radially-extending key formed on the segment to a keying slot of the fan and by welding the fan to the segment.
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The present invention is directed to improvement of electric machines and, more particularly, to an improved fan assembly of a dual internal fan alternator.
An automotive alternator typically converts mechanical energy being supplied by a motor to electrical energy for charging a battery and powering a vehicle's electrical system when the motor is running. The alternator may contain substantially all of its components inside a housing. For example, an alternator outputs an alternating current (AC) voltage to a set of rectifier diodes that convert the AC voltage to a direct current (DC) voltage. Additional electrical and electronic components (e.g., voltage regulator or ECU) may be provided within the alternator housing, and such components create heat. Eddy currents, core losses, and electrical resistances of brushes and rotor and stator coils create additional heat. The mechanical operation of an alternator further creates heat as a result of friction.
A field current may be supplied as an electrical input to the rotor windings by slip rings, and one or more DC voltages are output from the diode rectifiers. To provide a direct current output with low ripple, a three-phase stator winding may be used and the pole-pieces of the rotor may be shaped (e.g., claw-pole) to produce an AC stator output waveform similar to a square wave instead of a sinusoid. A claw-pole rotor core is typically formed with a drive end (DE) core piece and a slip ring end (SRE) core piece, where the respective poles of the two rotor core pieces are formed as opposed fingers interleaved with one another. In an alternative application, an alternator may be configured as a DC generator having a commutator.
Modern automotive alternators are generally required to supply ever-greater amounts of electrical current. For example, hybrid and electric vehicles may use electricity instead of internal combustion for driving the wheels, and an alternator may be combined with a starter in a mild hybrid configuration such as in a belt alternator starter (BAS) system. Other electrical loading from air conditioning, electric power steering, and other vehicle systems further increases the required alternator electrical capacity.
Efficiency of automotive alternators is generally limited by fan cooling loss, bearing loss, iron loss, copper loss, and the voltage drop in the diode bridges. The use of permanent magnets may increase efficiency by providing a more constant magnetic field and by guiding flux between rotor windings. An alternator may have dual internal fans to improve operating efficiency and durability and to reduce heat-related failures. The alternator housing may have air intake and exhaust apertures adjacent respective rear and front fans, thereby providing a cooling air flow. However, the fan portions of automotive alternators are not optimized for structural integrity.
SUMMARYIt is therefore desirable to obviate the above-mentioned disadvantages by providing a structure and method for improving the structural integrity of an alternator having dual internal fans.
According to an exemplary embodiment, an alternator having a center axis includes a drive end (DE) segment having a raised collar portion, a plurality of claw poles, an axially outward segment surface connecting the claw poles, and at least one key extending radially outward from the collar along the segment surface. The alternator also has a fan having an inside diameter formed as a ring, a keying slot extending radially outward from the ring, a plurality of blades, and a fan body connecting the blades and including a plurality of protrusions. The fan is mounted to the segment so that the collar fits inside the ring and the key fits inside the keying slot, and the fan is welded to the DE segment at the protrusions.
According to another exemplary embodiment, a method of cooling an alternator includes providing a drive end (DE) segment having a raised collar portion, a plurality of claw poles, an axially outward segment surface connecting the claw poles, and at least one key extending radially outward from the collar. The method also includes providing a fan having an inside diameter formed as a ring, a keying slot extending radially outward from the ring, a plurality of blades, and a fan body connecting the blades and including a plurality of protrusions. The method further includes placing the fan onto the segment so that the collar fits inside the ring and the key fits inside the keying slot, and welding the fan to the segment at the protrusions.
According to a further exemplary embodiment, a method of assembling a rotor of an alternator includes securing a fan to a drive end (DE) pole segment by mating a radially-extending key formed on the segment to a keying slot of the fan and by welding the fan to the segment.
The foregoing summary does not limit the invention, which is defined by the attached claims. Similarly, neither the Title nor the Abstract is to be taken as limiting in any way the scope of the claimed invention.
The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding or similar parts throughout the several views.
DETAILED DESCRIPTIONThe embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of these teachings.
In operation, when rotor 15 is rotated by an external driving force via pulley 22, a magnetic field is generated by the field winding 3 surrounding the field core, and the magnetic field passes circumferentially through the stator winding in conformance with the rotor rotation. Fans 34, 36, fixed to shaft 14, are rotated together with the field core, and blades 76 formed as cut-raised portions extending from fans 34, 36 are also rotated to produce cooling air flow inside electric machine 10.
The projection welding of assembly 42 may use very high current in short duration pulses, and a brazing material with thermally conductive additives may be used for filling gaps between fan 5 and segment 6. By comparison, conventional alternators may use TIG or laser welding to avoid a high temperature causing the degaussing of an alternator's permanent magnets. However, by separately manufacturing assembly 42, this conventional problem is avoided. The contacting metal surfaces of fan 5 and segment 6 are joined by the heat obtained from resistance to electric current flow. The surfaces may be held together under pressure exerted by welding electrodes (not shown). For example, copper alloy electrodes urge fan 5 and segment 6 together while simultaneously forcing a large current through projections 30, thereby melting the metal and forming welds. Heat is concentrated at projections 30, which permits the welding of the relatively heavier pole segment 6 and localizes the welds at projections 30. Any appropriate number of projections may be formed on fan 5, such as for closely spacing the individual welds. Projections 30 may also be utilized for positioning the workpieces. The welding electrode(s) are typically placed at or near dimples 17 so that the welding current is concentrated at underlying projections 30. When current pulses have a high magnitude and a short duration, the welds may be somewhat isolated to the general areas surrounding the respective projections 30. Keys 9 and keying slots 13 are thereby somewhat isolated from the welding.
A winding core section 44 may be formed as an integral part of pole segment 6, or it may be a separate component. In an alternative embodiment, the interior portion of pole segment 6 may include recessed portions 45, each circumferentially aligned with a key 9. For example, it may be desirable for the thickness of pole segment 6 to be uniform around its circumference, and the increased thickness of segment 6 at the raised keys 9 may be offset by reducing segment thickness under keys 9 by forming recess 45.
In
The interface of fan surface 31 and pole segment surface 11 may include applied or injected resin, nylon, adhesive, or other suitable thermally conductive material. The added material may provide a more stable and integral structure, may assist in balancing, and increases heat transfer out of the rotor core. Material(s) other than those used in brazing may be injected or otherwise applied to gaps and spaces in the fan/segment interface that remain after the welding process. For example, a curable thermally conductive material may be applied to segment surface 11 and/or fan surface 31 before welding, whereby the compression of surfaces 11, 31 against one another during welding causes the applied material to fill such gaps and spaces. The welding of projections 30, the press fitting of key slot 13 onto key 9, and the flow of filler material into unwelded gaps may occur simultaneously during manufacture when the welding electrodes act to clamp surfaces 11, 31 together, when a filler material is pre-applied to at least one of surfaces 11, 31, and when key slot 13 is properly seated as a result of the electrode compression or by other clamping.
The exemplary embodiments describe structure and methods of assembling a rotor of an alternator that include securing a fan to a drive end (DE) pole segment by mating a radially-extending key formed on the segment to a keying slot of the fan and by welding the fan to the segment. In alternative embodiments, one or more keys may be formed on a fan and corresponding keying slots may be formed on a pole segment. However, in such a case, welding at the keying interfaces is carefully controlled to assure that distortion of the fan and/or over-welding of fan portions at the projections does not occur.
While various embodiments incorporating the present invention have been described in detail, further modifications and adaptations of the invention may occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention.
Claims
1. An alternator having a center axis, comprising:
- a pole segment having a collar, a plurality of claw poles, an axially outward segment surface connecting the claw poles, and at least one key extending radially outward from the collar along the segment surface;
- a fan having an inside diameter formed as a ring, a keying slot positioned radially outward from the ring, a plurality of blades, and a fan body connecting the blades and including a plurality of protrusions;
- wherein the fan is mounted to the segment so that the collar fits inside the ring and the key fits inside the keying slot, and wherein the fan is welded to the segment at the protrusions.
2. The alternator of claim 1, wherein the at least one key comprises a plurality of keys symmetrically arranged about the center axis and the keying slot comprises a corresponding plurality of slots aligned with the keys and mated thereto.
3. The alternator of claim 2, wherein the protrusions are symmetrically arranged about the center axis.
4. The alternator of claim 1, wherein the keying slot comprises a pair of opposed axially-extending tabs.
5. The alternator of claim 1, wherein the key is mated to the keying slot by an interference fit.
6. The alternator of claim 1, wherein the collar is formed as an integral part of the segment.
7. The alternator of claim 1, wherein the protrusions are formed on an axially inward surface of the fan body.
8. A method of cooling an alternator, comprising:
- providing a pole segment having a raised collar, a plurality of claw poles, an axially outward segment surface connecting the claw poles, and at least one key extending radially outward from the collar;
- providing a fan having an inside diameter formed as a ring, a keying slot positioned radially outward from the ring, a plurality of blades, and a fan body connecting the blades and including a plurality of protrusions;
- placing the fan onto the segment so that the collar fits inside the ring and the key fits inside the keying slot; and
- welding the fan to the segment at the protrusions.
9. The method of claim 8, wherein the welding comprises brazing an interface of the fan and the segment.
10. The method of claim 8, further comprising placing a thermally conductive material at an interface of the fan and the segment.
11. The method of claim 8, wherein the welding comprises axially clamping the fan and segment toward one another.
12. The method of claim 8, wherein the keying slot includes a pair of axially extending tabs that engage the key, whereby the key is substantially isolated from the remainder of the fan.
13. The method of claim 12, wherein the welding comprises placing a welding electrode proximate the protrusions to thereby substantially isolate the welding to the protrusions.
14. The method of claim 13, further comprising filling gaps between isolated welds with a thermally conductive material.
15. The method of claim 8, wherein the key is secured inside the keying slot by press fitting.
16. The method of claim 15, wherein the welding and the press fitting are substantially simultaneous.
17. A method of assembling a rotor of an alternator, comprising securing a fan to a drive end (DE) pole segment by mating a radially-extending key formed on the segment to a keying slot of the fan and by welding the fan to the segment.
18. The method of claim 17, wherein the fan has an axially inward surface containing a plurality of projections, and wherein the welding comprises projection welding.
19. The method of claim 17, wherein the welding comprises brazing.
20. The method of claim 17, wherein the mating comprises press fitting a plurality of the radially-extending keys to a corresponding plurality of the keying slots.
Type: Application
Filed: Dec 5, 2012
Publication Date: Jun 5, 2014
Applicant: REMY TECHNOLOGIES, LLC (Pendleton, IN)
Inventors: Jiwon Chung (Fishers, IN), Scott Bitzer (Fishers, IN)
Application Number: 13/705,993
International Classification: F01D 5/30 (20060101);