U.S. patent application number 13/705993 was filed with the patent office on 2014-06-05 for front fan retention in dual internal fan alternator.
This patent application is currently assigned to REMY TECHNOLOGIES, LLC. The applicant listed for this patent is REMY TECHNOLOGIES, LLC. Invention is credited to Scott Bitzer, Jiwon Chung.
Application Number | 20140154086 13/705993 |
Document ID | / |
Family ID | 50825629 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140154086 |
Kind Code |
A1 |
Chung; Jiwon ; et
al. |
June 5, 2014 |
FRONT FAN RETENTION IN DUAL INTERNAL FAN ALTERNATOR
Abstract
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.
Inventors: |
Chung; Jiwon; (Fishers,
IN) ; Bitzer; Scott; (Fishers, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
REMY TECHNOLOGIES, LLC |
Pendleton |
IN |
US |
|
|
Assignee: |
REMY TECHNOLOGIES, LLC
Pendleton
IN
|
Family ID: |
50825629 |
Appl. No.: |
13/705993 |
Filed: |
December 5, 2012 |
Current U.S.
Class: |
416/213A ;
219/117.1; 228/101 |
Current CPC
Class: |
F01D 5/3061 20130101;
H02K 19/22 20130101; H02K 9/06 20130101 |
Class at
Publication: |
416/213.A ;
219/117.1; 228/101 |
International
Class: |
F01D 5/30 20060101
F01D005/30 |
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.
Description
BACKGROUND
[0001] The present invention is directed to improvement of electric
machines and, more particularly, to an improved fan assembly of a
dual internal fan alternator.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
SUMMARY
[0006] It 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0011] 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:
[0012] FIG. 1 is a schematic view of an electric machine;
[0013] FIG. 2 illustrates an exemplary twin internal fan
configuration and airflow resulting therefrom, in the exemplary
electric machine of FIG. 1;
[0014] FIG. 3 is an exploded perspective view of a fan aligned for
mounting to a pole segment, according to an exemplary
embodiment;
[0015] FIG. 4 is a schematic sectional view of a fan;
[0016] FIG. 5 is a perspective view of a key extending from the
collar of a pole segment of an alternator, according to an
exemplary embodiment;
[0017] FIG. 6 is a perspective view of a keying slot of a fan,
according to an exemplary embodiment;
[0018] FIG. 7 and FIG. 8 are respective inward- and outward-facing
perspective views of a pole segment assembly;
[0019] FIG. 9 is a partial sectional view taken along the line
IX-IX of FIG. 7; and
[0020] FIG. 10 is a perspective partial view of an electric
machine, according to an exemplary embodiment.
[0021] Corresponding reference characters indicate corresponding or
similar parts throughout the several views.
DETAILED DESCRIPTION
[0022] The 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.
[0023] FIG. 1 is a sectional view of an exemplary electric machine
10 having a rotor assembly 15 that contains several components
including a shaft 14, a field winding 3, and pole segments 1. A
case 16 encloses the machine's components and includes a front
bracket or drive end frame 18 and a rear bracket or slip ring end
(SRE) frame 20, which may be made of aluminum. Case 16 secures a
stator 4 to an inner wall surface of case 16. Shaft 14 is rotatably
supported by front bracket 18 via a first bearing 19 and by rear
bracket 20 via a second bearing 21. A pulley 22 is fixed to a first
end of shaft 14, enabling rotational torque from an engine to be
transmitted to shaft 14 by a belt (not shown). Slip rings 24 and
associated electrical conductors are provided for supplying an
electric current to rotor assembly 15. Slip rings 24 are fixed to
an end portion of shaft 14, and a pair of brushes 26 are housed in
a brush holder 28 disposed inside case 16 so as to slide in contact
with slip rings 24 to pass the electric current therethrough. A
voltage regulator (not shown) may be provided for adjusting the
magnitude of an alternating voltage generated in stator 4. A first
fan 34 and a second fan 36 are fixed to respective first and second
axial ends of the rotor assembly 15.
[0024] FIG. 2 is a sectional view of the electric machine of FIG.
1, illustrating an exemplary twin internal fan configuration and
airflow resulting therefrom. Respective front-end and rear-end air
intake apertures 80, 81 are disposed in respective axial end
surfaces of front bracket 18 and rear bracket 20, and front-end and
rear-end air discharge apertures 82, 84 are respectively disposed
in first and second outer circumferential portions of front bracket
18 and rear bracket 20. For example, the discharge apertures may be
adjacent to exposed conductor end turns 38 that extend axially from
stator core 4. The drive end, or first, fan 34 pulls air, generally
shown with arrows 67, axially into electric machine 10 through
inlet port 80 of front bracket 18. Most of the air is exhausted in
a radial direction, indicated with arrows 68, out of electric
machine 10 through outlet port 82 of the front bracket 18. Another
part of the air flow may continue in an axial direction 69 and then
exit out in a radial direction generally shown at 69', flowing out
through outlet port 84 of the rear bracket 16. On the SRE side, air
is drawn into the back of electric machine 10 by second fan 36 in
an axial direction indicated generally with arrows 70 and is then
exhausted primarily in a radial direction indicated generally with
arrows 70', flowing out through outlet port 84.
[0025] 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.
[0026] FIG. 3 is an exploded perspective view of a fan 5 aligned
for mounting to a pole segment 6, according to an exemplary
embodiment. The collar 7 of segment 6 is an annular, raised portion
having a center aperture 8 for receiving a shaft. A radially
extending key 9 may be integrally formed with pole segment 6 as a
portion raised from axially outward surface 11. Fan 5 has an
annular mounting ring 2 with a radially inward surface 12. Fan 5
also has a keying slot 13, and a number of dimples 17 spaced
circumferentially around fan surface 23. Fan 5 may be formed, for
example, by first stamping a sheet steel material such as carbonize
steel having corrosion resistance, and then bending the stamped
work piece to form fan blades 25. Alternatively, fan 5 may be cast
of steel or other suitable material. Fan blades 25 may vary in
number, height, shape, size, and angle, and they may be curved or
straight. The assembly includes placing fan 5 onto collar 7 and
then press fitting key 9 into keying slot 13. As a result, fan
inside surface 12 is placed around at least a portion of the
radially outward surface 27 of collar 7. Typically, embodiments
have at least two keys 9 and the same number of keying slots 13,
and such are arranged symmetrically about collar 7. For example,
two keys 9 may be 180.degree. apart, three keys 9 may be
120.degree. apart, four keys 9 may be 90.degree. apart, etc. The
multiple keys 9 and associated keying slots 13 are also typically
the same shape and size, so that the rotating assembly is
substantially balanced and symmetrical. After fan 5 has been
pressed onto segment 6, it is then welded in place and is further
pressed against segment 6 during the welding.
[0027] FIG. 4 is a schematic sectional view of a fan 5. When
dimples 17 are formed by stamping the outer fan surface 29,
projections 30 are thereby formed on inner fan surface 31. When fan
5 is pressed onto pole segment 6, projections 30 are thereby
pressed against axially outward pole segment surface 11. A welding
electrode (not shown) is attached to fan 5 and an opposite polarity
welding electrode is attached to pole segment 6. When electric
current of the welding flows between the electrodes, the resistance
at the interfaces of projections 30 and surface 11 creates heat at
the interfaces, and projections 30 are melted so that welds are
formed at the interfaces. The welding electrodes or other apparatus
may be used to urge fan 5 and segment 6 together during the welding
process, and brazing or other filling process may be utilized for
removing spaces or voids between the welded surfaces. For example,
the electrodes may provide clamping pressure and/or impacting force
while passing a current of 5000 to 100,000 amperes, at a voltage of
3.0 to 10.0 volts, with a duration of less than two seconds and a
duty cycle of five to ten percent. Any other suitable electric
current may be utilized, depending on a particular application. For
example, high frequency brazing/welding may be utilized when only a
shallow depth weld is required. Impacting and clamping surfaces may
be chosen for aligning the interfacing surfaces, for applying
pressure to develop proper surface resistance, for containing
molten metal, for forging the interfacing material, for
transferring electric current, for dissipating excessive heat,
and/or for cooling (e.g., by being water cooled). Processing may
include post weld heat cycling, and impacting and/or pressure
forging performed at any time. For example, a softening current may
be applied, followed by an impacting that compresses the softened
metal. A concurrent or subsequent impacting of fan 5 in proximity
to the softened interface acts to produce a higher degree of
coalescence or intimate joining by metallurgical union. Brazing
material may be applied to interface locations of pole segment
surface 11 by sputtering to prevent contamination, oxidation, and
other potential problems, although plating, vapor deposition, or
another process may alternatively be used. By way of non-limiting
example, a brazing material may include silver, phosphorous,
silicon, copper, nickel, tin, aluminum, magnesium, gold, zinc,
cadmium, and various alloys known in the art and typically chosen
depending on melting temperature range and flow properties at high
temperature. In contrast to conventional brazing, a flux, and
subsequent removal of its residue, may be unnecessary when the
brazing material already uniformly covers the interface area and
when the brazing material is being provided for localizing heat
rather than for being distributed by capillary action.
[0028] FIG. 5 is a perspective view of key 9 and FIG. 6 is a
perspective view of keying slot 13. Key 9 is formed as an integral
part of collar 7 which, in turn, may be formed as an integral
portion of pole segment 6. For example, a unitary pole segment 6
may be formed in a high temperature forging process. Key 9 may be
integrally formed with pole segment surface 11 or it may
alternatively be axially offset therefrom. A substantially oval
depression 32 is formed in segment surface 11, at a location
aligned with and radially outward of key 9. Depression 32 may be
used, for example, to provide access for a tool (not shown) for
applying force during press fitting to a proximate portion 33 of
fan surface 23 and/or to provide a depository for any weld nugget
or other substance such as brazing material that might interfere
with the mating between key 9 and keying slot 13. For example, slot
13 includes opposed axially extending tabs 35, 37 that respectively
press against and secure the lateral sides 39, 40 of key 9. By
creating space around such interface, the welding/brazing materials
are prevented from interfering. In addition, the space allows for
dimensional tolerances of key 9. For example, the space around
depression 32 may be utilized for radially positioning DE fan 5.
The extra space of keying slot 13 includes an aperture 41 through
fan center ring 2. By creating space around key 9 and fitting tabs
35, 37, keys 9 of the assembled structure act to prevent
circumferential movement of fan 5, with respect to segment 6,
without incurring undesirable axial or radial interference at the
keying interface. The extra space assures that welding does not
occur at the keying structures.
[0029] FIG. 7 and FIG. 8 are respective inward- and outward-facing
perspective views of a pole segment assembly 42, and FIG. 9 is a
partial sectional view taken along the line IX-IX of FIG. 7.
Assembly 42 is shown having only one key 9, but typically has at
least two keys arranged symmetrically. Fan 5 is secured to pole
segment 6 by the joinder of key 9 with fan keying slot 13 (FIG. 6)
and by welding at locations of dimples 17. Collar 7 has an exposed
collar portion 43 that extends axially beyond fan ring 2. Fan 5 is
typically not press fit against collar 7, and some space exists
between fan ring 2 and annular collar surface 27 (FIG. 5). Such
annular space allows the circumferential torque on fan 5 to be
concentrated at keys 9.
[0030] 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.
[0031] 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.
[0032] In FIG. 9, an exemplary sectional profile illustrates how
key 9 may be formed integrally with pole segment 6. Key 9 may have
a stepped profile in a radially outward direction, whereby a
portion of radially outward surface 27 of collar 7 extends axially
outward of key 9. The radially outward portion of key 9 may extend
axially inward of a nominal fan resting surface 31. For example,
fan surface 31 abuts pole segment surface 11 after the welding
process, and depression 32 prevents any binding around key 9 so
that fan surface 31 may lie flush against segment surface 11. When
properly seated, the axially outward side of key 9 is slightly
axially inward of fitting tab 35 and fitting tab 37 (FIG. 6), and
the radially outward end of key 9 is slightly spaced apart from fan
portion 33.
[0033] 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.
[0034] FIG. 10 is a perspective partial view of an electric machine
46, according to an exemplary embodiment. Fan 5 is secured to DE
pole segment 6 as described hereinabove. The rotation of shaft 14,
segment 6, and fan 5 creates a circumferential force between
segment 6 and fan 5, in parallel with the rotational direction 47,
usually but not always clockwise. Such circumferential force varies
with the changes in rotational speed and is affected by the
resistance to the corresponding movement by fan blades 25. As a
result of acceleration and fan blade resistance, rotational torque
on fan 5 is imparted onto keys 9. The tight fit of keys 9 with
corresponding keying slots 13 provides a centering function for DE
fan 5 and also prevents fan 5 from rotating relative to pole
segment 6. Increasing the widths, lengths, and heights of keys 9
acts to distribute the shear stresses imposed thereon. Typically at
least two or three keys 9 are provided to further distribute shear
stresses, and to prevent relative radial movement of fan 5
respecting segment 6. Axial movement of fan 5 relative to segment 6
is prevented by the welds at the axially inward fan projections 30
(FIG. 4) that are aligned with dimples 17.
[0035] 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.
[0036] 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.
* * * * *