BRUSHLESS ALTERNATOR
FIELD OF THE INVENTION:
[0001] The present invention relates to alternators, and particularly to brushless alternators.
Typically, brushless alternators are found in automobiles, driven by the automobile engine for
purposes of re-charging the automobile battery. However, the brushless alternators of the present
5 invention may also find use as single-phase or multi-phase alternating current generators to be
employed in aircraft and the like. The present invention provides high energy output per unit
volume, so as to be compact in size.
BACKGROUND OF THE INVENTION:
10 [0002] Brushless alternators, particularly of the sort which may be employed in automobiles
for purposes of re-charging automobile batteries, are well known. However, brushless alternators
are not necessarily employed in significant numbers because the known prior art brushless alternators
tend to be complicated in structure and large in size, particularly when considered in terms of energy
output per unit volume. Accordingly, brush-type alternators still find significant use.
15 [0003] Of course, brush-type alternators are much more subject to failure than brushless
alternators which, apart from a rotor which is journaled or otherwise secured for rotation with a drive
shaft, employs essentially no moving parts, and no parts which move in contact one with another
such as a brush in a commutator slip ring assembly, or the like.
[0004] By their nature, alternators will generate alternating current in the first instance.
20 Typically, that alternating current is rectified so as to be employed for purposes of re-charging an
automotive battery. However, depending on the number and nature of the windings employed, their
structure, and other well known factors, a significant and useful alternating current voltage can be
generated in an alternator. That source of alternating current may find use in many non-automotive
circumstances, such as in aircraft or the like.
25 [0005] However, the energy output per unit volume of prior art alternators has generally been
quite low, resulting in substantially massive alternator structures which might not be usefully
employed due to the penalty of their own weight.
2
[0006] The present inventor has quite unexpectedly discovered that by proper orientation and
placement of stator winding coils, and placement of a segmented rotor having segments at each side
of the wound stator coils, high energy yield per unit volume is attainable.
[0007] Several known disadvantages of prior art alternators are, of course, their employment
5 of wearable subassemblies such as the brush sub-assembly and a slip ring sub-assembly. While it
would seem to be apparent that elimination of those two wearable sub-assemblies should reduce
manufacturing cost and assembly design, the contrary seems to have been the case in the prior art.
[0008] Another disadvantage of the prior art is typically that the voltage imposed on the
stationary field coil is limited by the size and construction of brush and slip ring sub-assemblies,
10 because the field coil is mounted on a rotor. As will be noted hereafter, that disadvantage is
overcome by the brushless alternator of the present invention.
[0009] A still further disadvantage of the prior art is that most structures are not capable of
fully engaging the magnetic flux during relative motion of the magnetic fields with respect to the
induction windings in which electrical current is induced.
15 [0010] The present inventor has also unexpectedly discovered that the operating principals
of the present invention may be manifested in brushless alternators which have either an axial
configuration, with the rotor and stator elements being axially aligned with respect to the drive shaft;
or, the rotor and stator elements may be radially aligned with respect to the drive shaft. Each has its
own advantages, as discussed in greater detail hereafter.
20
DESCRIPTION OF THE PRIOR ART:
[0011] Certain prior art patents relating to alternator structures, particularly multi-phase and
brushless structures, have been noted, as follows:
[0012] Tiltins United States Patent 3,571,639 issued March 23, 1971, provides a dual-action
25 brushless alternator having two annular stators, and having direct current excitation windings
between the magnetic end sections of the housing and the stators, and between the two stators. A
common polyphase alternating current winding is wrapped about both stators in one embodiment,
and in another embodiment two separate polyphase windings are placed on the respective stators.
Diode networks are provided so as to attain a relatively high direct current output voltage.
3
[0013] Barrett United States Patent 3,953,753 issued April 27, 1976 teaches a three-phase
alternator which is particularly suited for automotive use. Three stator winding sections each include
a given number of coils, with each coil encompassing two stator poles and being separated from the
next coil in the section by an unwound pole. The rotor poles are of tapered construction. A direct
5 current excitation coil encompasses a tubular centre leg of a stationary magnetic core which has an
E-shaped configuration, with flux of one polarity going to the rotor partly through the shaft and
through a radial air gap having substantial surface area. The flux of the opposite polarity goes to the
rotor through a large-area radial air gap adjacent outer flange of the core.
[0014] United States Patent 4,075,519 issued February 21, 1978 to Mrcun teaches an
10 alternator which has an axially split housing with two symmetrical halves into which the rotor shaft
is journaled. Parts of stator teeth are held between the two housing halves, and co-act with relatively
offset sets of rotor poles mounted on a shaft, the teeth being interconnected inside or outside of the
rotor by an annular magnetic yolk. There is a stationary excitation coil surrounding a split inner yolk
of the rotor body, which is carried within the rotor by the yolk or by tooth-supported ring. The teeth
15 have wings which are closely spaced from orbital paths of the poles, and have webs which are about
half as wide as their wing span, and the teeth are enveloped by armature windings in which the
output voltage of the alternator is induced when the rotor is turned.
[0015] Barrett United States Patent 4,307,309 issued December 22, 1981 teaches a different
structure than his ‘753 patent noted above. A brushless alternator which is particularly adapted for
20 automotive use comprises a field coil mounted on the centre leg of a stationary core, with a rotor
shaft extending through the centre leg of the core. A first disc-shaped rotor member is mounted on
the shaft and faces the centre leg of the core across a large-area axial air gap, and has a first set of
radially projecting rotor poles. A second, annular rotor member is mounted on the first rotor member
and faces an outer flange portion of the core across a second large-area axial air gap. It has a second
25 set of axially projecting rotor poles interleaved one-for-one with the first set. The two sets of rotor
poles have pole faces which are aligned in a common radial plane facing an annular array of stator
poles across a third large-area axial air gap which is arranged for balance of the magnetic attraction
forces to which the rotor is subjected. The coils of the stator winding are wound in an even number
of layers, alternately outside-in and inside-out, with the corresponding layers of adjacent coils being
4
interconnected, so as to afford maximum current capacity in coils of minimum axial length, and
thereby keeping the axial length of the stator poles to a minimum.
[0016] Godkin et al United States Patent 4,611,139 issued September 9, 1986 teaches an
axial air gap brushless alternator which has a stationary field coil and core surrounded by a stationary
5 stator coil and core with a cylindrical air gap between them. The rotor assembly is fixed to a
rotatable shaft and has interweaved separate magnetic finger assemblies joined by a non-magnetic
ring, so that the fingers are rotated in the cylindrical gap. The stator and field coils are radially
disposed with respect to the shaft. The field coil axially extends beyond the effective axial length
of the field coil and provides at an axial position beyond the effective axial length of the filed coil
10 at least one low reluctance axial flux gap between the field core and the magnetic fingers. The
purpose of the flux gap is to conduct a substantial portion of the flux created by the field coil. The
field coil also serves as the shaft bearing retainer and has a bearing grease reservoir comprising a
cylindrical recess adjacent the shaft bearing.
[0017] Giuffrida United States Patent 4,647,806 issued March 3, 1987 teaches a brushless
15 alternator which has interconnected stator coils disposed in stator plates which surround the main
winding of the rotor and include rectifiers coupled to the stator coils. The rotor is on a shaft which
is supported within the housing of the alternator and includes an exciter with shaft-mounted rectifiers
for supplying DC voltage to the main winding of the rotor. The exciter field coil is spool wound on
a cylindrical core that is contained within the exciter stator that is attached to the alternator housing.
20 The field coil has a concentric opening for slidably receiving the rotor shaft. The exciter rotor
armature does not rotate, and is affixed to the alternator housing and surrounds the outer periphery
of the exciter field coil. The main winding of the rotor has a cylindrical sleeve which extends from
one end to engage and support the exciter rotor armature in alignment with the exciter stator.
[0018] Lindgren United States Patent 4,831,300 issued May 16, 1989 teaches a brushless
25 alternator and synchronous motor structure which provides varying-reluctance paths for radially
directed, unidirectional magnetic fields by means of a rotor-stator configuration in which the innerand
outer-rotor poles and a rotor-pole connecting means surround one end and the inner- and outercylindrical
surfaces of a hollow cylindrical stator. One of the inner or outer poles includes a field
5
concentrator member. Optionally, an excitation field may be provided by a stationary winding which
requires no brushes for energizing, or by permanent magnetization.
[0019] Heinrich et al United States Patent 4,918,343 issued April 17, 1990 teaches a
brushless alternator structure that is particularly concerned with cooling the structure when mounted
5 to an automotive engine. Raised ribs define an internal bore of the housing, which has a constant
diameter to mount the stator and exciter field assemblies, both of which have the same laminations.
Ribs also define cooling airflow paths through the housing, and a fan is mounted outside of the
housing at the free end thereof to draw air into the engine and through the housing and out the free
end thereof.
10 [0020] Woodward, Jr. United States Patent 6,066,908 issued May 23, 2000 teaches another
disc-type brushless alternator with a shaft rotatably attached to the alternator housing, and having
a plurality of rotors and a pulley at one end. The rotors and stators have serrated surfaces so that the
serrated surfaces of the rotors and of the stators face each other and define an axial air gap
therebewteen.
15 [0021] Tupper et al United States Patent 6,177,746 issued January 23, 2001 teaches a low
inductance electrical machine which may be an alternator or a motor, and having a low armature
inductance. Complimentary armature windings are arranged so that fluxes induced by currents in
the armature winding effectively cancel, thereby leading to low magnetic energy storage within the
machine. This leads to low net flux levels, low core losses, low inductance, and reduced tendency
20 toward magnetic saturation. By including additional gaps in the magnetic circuit, independent
adjustment of air gap geometry is allowed, together with independent adjustment of armature
inductance. Separately excited field arrangements allow rotor motion to effect brushless alternator
or brushless motor operation. Typically, the stator includes two annular rings and a concentric field
coil, together with a rotor structure which is separated from the stator by four air gaps.
25
SUMMARY OF THE INVENTION:
[0022] In its broadest principles, the present invention provides a brushless alternator which
comprises a housing, a rotatable drive shaft, a stationary field coil, a stator having a plurality of coils
wound on a plurality of laminated cores, a segmented rotor mounted for rotation with the drive shaft,
6
electrical leads for supplying a source of direct current electricity to the stationary field coil, and
electrical leads for conducting induced electrical currents away from the plurality of stator coils.
[0023] The segmented rotor is made from a magnetizable material, and has a U-shaped crosssection
which comprises a pair of opposed segmented discs and a connecting base portion
5 therebetween at a first, closed end of the segmented rotor.
[0024] Each segmented disc comprises n segments which extend away from the closed end
thereof, and the segments in each of the two segmented discs are aligned with each other. That is
to say, the segments in each of the two segmented discs are opposed one to the other in each
instance.
10 [0025] The stationary field coil is located near the closed end of the segmented rotor between
the pair of segmented discs; so that, when the stationary field coil is energized with direct current
electricity, each pair of aligned segments of the opposed segmented discs of the rotor comprises a
pair of opposite polarity magnetic poles, and so that a directed magnetic field exists between each
pair of aligned segments.
15 [0026] The combined directed fields of all of the pairs of aligned segments are thereby
directed from one of the segmented discs to the other of the segmented discs.
[0027] There are at least 2n coils wound on 2n laminated cores arranged within the housing,
so as to be located at the end of the segmented rotor opposite the first, closed end thereof.
[0028] The 2n coils and the 2n laminated cores are fully distributed and are placed adjacent
20 one another between the segmented discs of the rotor.
[0029] The distance between each segment on each of the segmented discs, and the spaces
therebetween, are substantially equal at any point along the length thereof, at least in the region
thereof where the coils are located between the segmented discs.
[0030] The widths of each of the wound coils are substantially equal at any point along the
25 length thereof.
[0031] Each alternate coil is wound in clockwise fashion, and each interposed coil is wound
in counterclockwise fashion.
7
[0032] Typically, but not necessarily, the brushless alternator of the present invention will
further comprise a rectifier to which the induced electrical currents from the plurality of stator coils
are fed, and from which generated direct current electricity is taken.
[0033] The brushless alternator structure of the present invention also may include m sets of
5 2n coils and m sets of 2n laminated cores.
[0034] Each set of coils is laterally offset with respect to one another, so as to be evenly
distributed about the stator.
[0035] The sets of coils are arranged sequentially between the segmented discs of the rotor.
[0036] The sets of laminated cores are aligned one with another between the segmented discs
10 of the rotor.
[0037] One of each of the sets of coils is wound over one of each of the sets of laminated
cores.
[0038] Typically, in the brushless alternator of the present invention, n is an even number
between 4 and 20 – for example, 10 – and m is an integer between 2 and 6 – typically, 3–.
15 [0039] Typically, the material of this segmented rotor is mild steel.
[0040] In an axial configuration of the brushless alternator of the present invention, there is
further provided a spacer ring on which the rotor is mounted.
[0041] The pair of opposed segmented discs of the rotor are thereby axially aligned with
respect to the drive shaft; and the plurality of coils and the plurality of laminated cores are also
20 axially aligned with respect to the drive shaft.
[0042] In the axial configuration of the brushless alternator of the present invention, typically
the stator comprises a cylindrical heat sink on which each of the stationary field coil and the plurality
of coils which are wound on the plurality of laminated cores, are respectively mounted.
[0043] The axial configuration of the present invention may further comprise a pair of
25 stabilizer rings of non-magnetic material, which are mounted on each of the segmented discs of the
rotor at the ends of the segments opposite the closed end.
[0044] In a radial configuration of brushless alternator of the present invention, the pair of
opposed segmented discs of the rotor are radially aligned with respect to the drive shaft; and the
8
plurality of coils and the plurality of laminated cores are radially aligned with respect to the drive
shaft.
[0045] In the radial configuration of the present invention, the stator may further comprise
a disc-shaped heat sink on which each of the stationary field coil and the plurality of coils wound on
5 the plurality of cores are respectively mounted.
BRIEF DESCRIPTION OF THE DRAWINGS:
[0046] The novel features which are believed to be characteristic of the present invention,
10 as to its structure, organization, use and method of operation, together with further objectives and
advantages thereof, will be better understood from the following drawings in which a presently
preferred embodiment of the invention will now be illustrated by way of example. It is expressly
understood, however, that the drawings are for the purpose of illustration and description only and
are not intended as a definition of the limits of the invention. Embodiments of this invention will
15 now be described by way of example in association with the accompanying drawings in which:
[0047] Figure 1 is an elevation, partially in cross-section, of a first embodiment of the
present invention, showing a brushless alternator having an axial configuration;
[0048] Figure 2 is a section taken along arrows 2-2 in Figure 1;
[0049] Figure 3 is an elevation, partially in cross-section, of a second embodiment of the
20 present invention, showing a brushless alternator having a radial configuration;
[0050] Figure 4 is a section taken along arrows 4-4 in Figure 3;
[0051] Figure 5 is an exploded assembly view of the embodiment of Figure 3;
[0052] Figure 6 is a view to a larger scale of the portion identified at “6" in Figure 5;
25
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0053] The novel features which are believed to be characteristic of the present invention,
as to its structure, organization, use and method of operation, together with further objectives and
advantages thereof, will be better understood from the following discussion.
9
[0054] As noted, the present invention is particularly manifested in two different
configurations – an axial configuration where the rotor and stator are aligned axially with respect to
the drive shaft, and a radial configuration where the rotor and stator are aligned radially with respect
to the drive shaft. However, both embodiments of the present invention share a considerable number
5 of components in common, and the same reference numerals are used to identify similar components
throughout the figures of drawings herein.
[0055] The first embodiment of the present invention is identified at 100 in Figure 1; the
second embodiment is identified at 200 in Figures 3 and 5. Each embodiment 100 and 200
comprises a two-part housing, having housing shells 12 and 14. Typically, the depth of housing shell
10 14 is greater than the depth of housing shell 12. A rotatable drive shaft 16 is provided, on which
pulley 18 is mounted so as to provide rotational driving force to the brushless alternator. Typically,
especially when the alternator is employed for use in an automobile or other vehicle, a drive belt is
wrapped around the pulley 18 to receive driving force from the engine. In other uses, the rotational
driving force imparted to the pulley 18 and drive shaft 16 may come from different sources.
15 [0056] Each embodiment 100 and 200 of the brushless alternator of the present invention
includes a stationary field coil 20. The stationary field coil 20 forms part of a stator assembly which
also includes a plurality of coils shown generally at 22, and which are mounted on a plurality of
laminated cores which are indicated generally at 24.
[0057] A segmented rotor is shown generally at 26, and in each embodiment 100 and 200
20 the segmented rotor 26 is mounted for rotation with the drive shaft 16.
[0058] Electrical leads 28 are provided for supplying a source of direct current electricity to
the stationary field coil 20; and electrical leads 30 are provided for conducting the induced electrical
currents which will occur during operation of the brushless alternator, away from the plurality of
stator coils 22.
25 [0059] It will be seen that the housing 12, 14 is mounted using appropriate bearings 102, 104
against the drive shaft 16. For cooling purposes, of the housing 12, 14 is typically provided with a
plurality of vents or cooling apertures 106.
[0060] Each of the segmented rotors 26 is made from a magnetizable material – typically,
mild steel. Each of the segmented rotors has a U-shaped cross-section, as can be seen in Figures 1
10
and 3. The specific construction of the segmented rotor 26 in the embodiments 100, 200 is
somewhat different, in that the segmented rotor 26 in the embodiment 200 of the radially directed
rotor and stator actually comprises two pieces, as will be noted hereafter.
[0061] The segmented rotor 26 of the axial embodiment 100, shown in Figures 1 and 2,
5 comprises a pair of opposed segmented discs 32, 34, and the connecting base portion 36 at a first,
closed end of the segmented rotor 26. It will be seen in Figure 1 that the rotor structure is essentially
a one piece rotor having a generally horseshoe-shaped configuration 32, 36, 34.
[0062] The segmented rotor 26 of the radial configuration embodiment 200 comprises two
separable opposed segmented discs 40 and 42, and has a closed end at 44. Nonetheless, the
10 segmented rotor 26 of the radial embodiment 200 of brushless alternator in keeping with the present
invention also has a U-shaped cross-section, as can be seen in Figure 3.
[0063] Each of the segmented discs 32, 34, or 40, 42, comprises n segments or fingers. A
typical segment 46 can be seen in Figure 1 of the axial embodiment 100, and the ends 48, 50 of each
of the segments 46 are shown in Figure 2. Typical segments 52 of the segmented discs 40, 42 of the
15 radial embodiment 200 of brushless alternator in keeping with the present invention, are shown in
each of Figures 4, 5, and 6.
[0064] It has been noted that there are n segments 46 or 52 which extend away from the
closed end 36 or 44 of the respective segmented rotor 26. Each of those segments 34 or 52 is aligned
with the respective segment 34 or 52 in the other of the segmented discs 32, 34 or 40, 42.
20 [0065] It will be noted in each of Figures 1 and 3 that the stationary field coil 20 is located
near the respective closed end 36 or 44 of the respective segmented rotor structure 26 of
embodiments 100 or 200. Accordingly, when the stationary field coil is energized with direct current
electricity through its leads 28, it is evident that each pair of the aligned segments 46 or 52 of the
opposed segmented discs 32, 34, or 40, 42 respectively, comprises a pair of opposite polarity
25 magnetic poles. This is seen particularly in Figure 2. Thus, there is a directed magnetic field which
exists between each of the pair of aligned segments 46 or 52, respectively. This is also shown
particularly in Figure 2, where in the embodiments shown, all of the interior ends 50 of the
respective segments 46 have a south pole polarity; and all of the outer ends 48 of the respective
11
segments 46 have a north pole polarity. The same will be true of course, in the radial configuration
of the present invention, shown in Figures 3 through 6.
[0066] Obviously, therefore, the combined directed fields of all of the pairs of aligned
segments 46 or 52 are directed from one of the segmented discs 32 or 34, or 40 or 42, to the other
5 of the segmented discs 34 or 32, or 42 or 40, respectively.
[0067] A feature of the present invention is that while there are n segments 46 or 52 on each
of the segmented discs 32, 34 or 40, 42, there are at least two n coils which are wound on 2n
laminated cores that are arranged within the housing 12, 14, so as to be located at the end of the
segmented rotor 26 opposite the respective first, closed end 36 or 44 thereof, as seen in Figures 1 and
10 3. As will be made clear hereafter, where there are simply 2n coils wound on 2n laminated cores,
the alternator will function as a single-phase alternator; it will also be seen hereafter that typically
there are enough coils and laminated cores so as to provide a multi-phase operation.
[0068] In any event, each of the 2n coils 22 and the 2n laminated cores 24 are fully
distributed and are placed adjacent one another between the segmented discs 32, 34 or 40, 42 of the
15 respective segmented rotor 26. In other words, as can be seen in Figures 2 and 4 through 6, there is
essentially no space between the adjacent coils 22, so that they are fully distributed around the stator
structure.
[0069] The geometry of each of the embodiments 100, 200 of brushless alternator in keeping
with the present invention is such that the distance between each of the segments 46 or 52 on each
20 of the segmented discs 32, 34 or 40, 42, and the spaces between the respective segments 46 or 52,
is substantially equal at any point along the length thereof, at least in the region thereof where the
coils 22 are located between the segmented discs 32, 34 or 40, 42. As can be understood, in the axial
embodiment 100, shown in Figures 1 and 2, the spacing between each of the segments is
substantially constant, at least in the region where the segments underlie or overlie the coils 22. The
25 segments 52, and the spaces between them, in the embodiment 200, are tapered outwardly, but each
is substantially equal at any point along the length of any segment 52 or the spaces between them.
Moreover, the width of each of the wound coils 22 are substantially equal at any point along the
length thereof. Once again, those widths are substantially constant in the embodiment 100, and taper
in the embodiment 200, as can be seen particularly in Figures 4 and 6.
12
[0070] Finally, a specific provision of the present invention is that each alternate coil in each
set of coils on each set of cores, is wound in clockwise fashion, and each interposed coil is wound
in counterclockwise fashion. Thus, the coils 60a, 60b, and 60c shown in Figure 2 are each wound
in clockwise fashion – that is, up on the left and down on the right, as viewed in Figure 2; whereas
5 the coils 70a, 70b, and 70c are wound in counterclockwise fashion – that is, down on the left and up
on the right, as viewed in Figure 2.
[0071] Likewise, each of the coils 62a, 62b, and 62c of the embodiment 200, as seen
particularly in Figure 6, is wound in clockwise fashion – up on the left and down on the right, as
viewed in Figure 6; and each of the coils 72a, 72b, and 72c is wound in counterclockwise fashion
10 – down on the left and up on the right, as viewed in Figure 6.
[0072] Typically, but not necessarily, each brushless alternator 100 or 200 in keeping with
the present invention further comprises a rectifier assembly 56, whose purpose is to receive the
alternating electric current from the windings 22 – that is, the windings 60a, 60b, 60c and 70a, 70b,
70c or 62a, 62b, 62c and 72a, 72b, and 72c – so as to provide a direct current output from the
15 brushless alternator of the present invention. A direct current output may be used in an automotive
vehicle for purposes of providing charging current for the battery. However, as also noted, there may
be other instances where the rectifier will not be required, because the alternator may be configured
so as to provide an alternating current output – usually, a multi-phase output as discussed hereafter.
[0073] As noted, the embodiments which are shown in the figures are multi-phase
20 embodiments. Indeed, they are three-phase embodiments. It will be evident that a single set of
windings may be provided for single-phase output, but multi-phase output is typically more efficient,
especially due to rectification losses and the like.
[0074] Considering any single layer of windings 60a, 70a, for example, in Figure 2, it will
be seen that there are, indeed, twice as many coils 60a, 70a, as there are segments 46. Thus, for each
25 layer an alternating current will be induced, in the manner now described.
[0075] Again, having particular regard to Figure 2, and considering only the inner layer of
coils comprising coils 60a, and 70a, as a pair of segments 46 – indicated by their ends 48 and 50 in
Figure 2 – passes toward and over clockwise coil 60a, one polarity of electric current will be induced
in that coil. Then, as the same pair of magnetic field segments 46 recedes away from that coil 60a
13
as the magnetic field passes it, the opposite polarity of current will be induced in the coil.
Obviously, if all of the coils were wound in the same orientation, and packed tightly as is shown and
as is the standard, induction of electric current between neighbouring coils would collide. That is
to say, any segment of the north and south field between any two segments 46, as shown at 48 and
5 50, would be in the process of approaching a coil 60a while receding away from a coil 70a.
[0076] However, by winding the coil 60a in clockwise fashion, as noted, and winding the coil
70a in counterclockwise fashion, as noted above, the same polarity induction of electric current in
any two neighbouring coils will be allowed as the field segments of the rotating electro-magnetic
field passes towards and away from those coils. The reversal of the induction polarity which occurs
10 over the centres of each of the coils 60a and 70a will occur, but in the opposite directions.
[0077] Accordingly, a very high output of energy per unit volume may be achieved. This,
of course, is made even more advantageous when an embodiment such as that shown in Figures 2
and 6 is employed, where there are three layers of coils.
[0078] Typically, prior art alternators employ a different arrangement of rotor. Typically,
15 alternate segments are of opposite polarities, and are separated one from the other by the use of nonmagnetic
materials. This results in a magnetic field which is oriented tangentially, more or less
parallel to the windings of the stator coil, rather than directly perpendicular to the windings of the
stator coil as found in the present invention.
[0079] If, in an embodiment such as those shown in any of the figures herein, there are n
20 segments 46 or 52 – ten as shown in each of the embodiments 100 and 200 as illustrated – then there
are at least 2n or 20 coils which are wound on 2n or 20 laminated cores.
[0080] However, as it happens, each of the embodiments which is illustrated in the present
discussion is shown as being a three-phase embodiment, where there are m sets of 2n coils and m sets
of 2n laminated cores – that is, there are three sets of 20 coils and three sets of 20 laminated cores.
25 [0081] As can be seen in each of Figures 2 and 6, in particular, each of the sets of coils – say,
60a, 60b, 60c – is laterally offset with respect to one another so as to be evenly distributed about the
stator assembly.
[0082] Obviously, the sets of coils 60a, 60b, 60c and 70a, 70b, and 70c, are arranged
sequentially between the segmented discs 46 of the segmented rotor 26 from in to out as seen in
14
Figure 2. Each of the sets of laminated cores 24, on the other hand, are radially aligned one with
another between the segmented discs of the rotor, in the embodiment of Figures 1 and 2; and each
of the sets of laminated cores 24 are axially aligned one with another in the embodiment of Figures
3 to 6.
5 [0083] Accordingly, one of each of the sets of coils 60a, 60b, 60c, 70a, 70b, and 70c, is
wound over one of each of the sets of laminated cores. This is clearly seen in each of Figures 2 and
6, where each coil is wound over three cores 24; and the cores are aligned one with each other,
whereas the coils are staggered or offset one with respect to the other.
[0084] Typically, there may be between four and twenty segments 46 or 52; and if the
10 brushless alternator is not a single-phase alternator it may be typically between two and six phases,
usually three phases.
[0085] In the embodiment of Figures 1 and 2, being that of an axial configuration, there is
also included a spacer ring 64.
[0086] As seen in Figure 1, the segmented rotor 26 is keyed to the spacer ring 64 so as to be
15 spaced therefrom and so as to be aligned axially with respect to the drive shaft 16. Obviously, as
noted, the segmented discs 32, 34, and the windings 22 with their cores 24, are all axially aligned
with respect to the drive shaft 16.
[0087] Typically, the axial configuration as shown in Figures 1 and 2 is such that the stator
which comprises the stationary field coil 20 and the wound coils 22 and their cores 24 are mounted
20 on a cylindrical heat sink 66.
[0088] Also, for purposes of stability, there may be a pair of stabilizer rings 74, 76 which are
mounted on each of the segmented discs 32, 34, respectively, at their ends 48 and 50 which are
opposite the closed end 36.
[0089] In the embodiment of Figures 3 to 6, where the stator and rotor assemblies are aligned
25 radially with respect to the drive shaft 16, the windings 22 and their cores 24, and the stationary field
coil 20, are typically mounted on a disc shaped heat sink 78.
[0090] Of course, the precise structure of the stator assemblies may not necessarily employ
the heat sink 76 or 78, provided that the stator assemblies are mounted in place with respect to the
housing 12, 14 in such a manner that the stationary field coil 20 and the windings 22 and their cores
15
24 – as specifically discussed above – are appropriately place with respect to the segments 46 or 52
of the respective segmented discs 32, 34 or 40, 42.
[0091] As previously noted, several advantages accrue from the brushless alternator
embodiments described herein. The first is that two wearable sub-assemblies, the brush assembly
5 and the slip ring assembly, of a typical alternator of the sort generally used at the present time in
automotive vehicles, have been eliminated. This provides a reduction in manufacturing cost; but as
can be seen, the present invention also provides simplification of design and assembly.
[0092] Since the brushes and slip rings have been eliminated, then there is no specific
limitation as to the voltage which may be imposed on the stationary field coil.
10 [0093] Finally, the present invention provides for an even and full engagement of the
magnetic flux which is utilized for the induction of an alternating electric current in the stator
windings. This permits for a lower current in the stationary field coil to establish comparable flux
utilized for induction of electric current, as compared to present day automotive vehicle alternators.
Again, this leads to lower manufacturing costs because of lower material costs.
15 [0094] Still further, the present invention provides for a quite high generated electrical
current or energy density per unit volume, due to the compact nature of the designs of either
embodiment of brushless alternator 100 or 200, and the fact that there is no unnecessary employment
of unwound poles, non-magnetic spacer materials, and the like.
[0095] Each of the embodiments of the present invention provides certain advantages. For
20 example, the embodiment of Figures 1 and 2 – the axial configuration 100 – allows for simple
disassembly and repair, simply by removal of the housing shell 12 so as to repair or replace any of
the windings, stationary field coil, rectifier assembly, and so on. The disadvantage of the
configuration of Figures 1 and 2, if it can be called a disadvantage, is the requirement for the use of
the spacer ring 64.
25 [0096] The embodiment of Figures 3 to 6 overcomes that disadvantage; but it will be seen
that repair and disassembly require removal of the entire housing shells 12 and 14. On the other
hand, the manufacturing process to produce the rotor assembly, comprising the discs 40 and 42, is
simpler than that of providing the rotor assembly of the embodiment of Figures 1 and 2.
16
[0097] There has been described several embodiments of brushless alternators, which may
function in single-phase or multi-phase mode, and which provide high output energy density per unit
volume.
[0098] Other modifications and alterations may be used in the design and manufacture of the
5 apparatus of the present invention without departing from the spirit and scope of the accompanying
claims.
[0099] Moreover, the word "substantially" when used with an adjective or adverb is intended
to enhance the scope of the particular characteristic; e.g., substantially planar is intended to mean
planar, nearly planar and/or exhibiting characteristics associated with a planar element. Specifically,
10 substantially equal is intended to convey the meaning of equality or near equality, without the
requirement for absolute exactness.
[00100] Throughout this specification and the claims which follow, unless the context requires
otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be
understood to imply the inclusion of a stated integer or step or group of integers or steps but not to
the exclusion of any other integer or step or group of integers or steps.
17
WHAT IS CLAIMED IS:
1. A brushless alternator comprising a housing, a rotatable drive shaft, a stationary field
coil, a stator having a plurality of coils wound on a plurality of laminated cores, a segmented rotor
mounted for rotation with said drive shaft, electrical leads for supplying a source of direct current
electricity to said stationary field coil, and electrical leads for conducting induced electrical currents
5 away from said plurality of stator coils;
wherein said segment rotor is made from a magnetizable material, and has a U-shaped
cross-section comprising a pair of opposed segmented discs and a connecting base portion
therebetween at a first, closed end thereof;
wherein each segmented disc comprises n segments extending away from said closed
10 end, and the segments in each of said two segmented discs are aligned with each other;
wherein said stationary field coil is located near said closed end of said segmented
rotor between said pair of segmented discs; whereby, when said stationary field coil is energized with
direct current electricity, each pair of said aligned segments of said opposed segmented discs
comprises a pair of opposite polarity magnetic poles, and a directed magnetic field exists between
15 each said pair of aligned segments; and whereby the combined directed fields of all of said pairs of
aligned segments are directed from one of said segmented discs to the other of segmented discs;
wherein there are at least 2n coils wound on 2n laminated cores arranged within said
housing so as to be located at the end of said segmented rotor opposite said first, closed end thereof;
wherein said 2n coils and said 2n laminated cores are fully distributed and are placed
20 adjacent one another between said segmented discs of said rotor;
wherein the distances between each said segment on each of said segmented discs,
and the spaces therebetween, are substantially equal at any point along the length thereof, at least in
the region thereof where said coils are located between said segmented discs;
wherein the widths of each of said wound coils are substantially equal at any point
25 along the length thereof; and
18
wherein each alternate coil is wound in clockwise fashion, and each interposed coil
is wound in counterclockwise fashion.
2. The brushless alternator of claim 1, further comprising a rectifier to which said
induced electrical currents from said plurality of stator coils are fed, and from which generated direct
current electricity is taken.
3. The brushless alternator structure of claim 1, wherein there are m sets of 2n coils and
m sets of 2n laminated cores;
wherein each of said sets of coils is laterally offset with respect to one another so as
to be evenly distributed about said stator;
wherein said sets of coils are arranged sequentially between said segmented discs of
said rotor;
wherein said sets of laminated cores are aligned one with another between said
segmented discs of said rotor; and
wherein one of each of said sets of coils is wound over one of each of said sets of
laminated cores.
4. The brushless alternator of claim 3, where n is an even number between 4 and 20, and
m is an integer between 2 and 6.
5. The brushless alternator of claim 4, where n is 10, and m is 3.
6. The brushless alternator of claim 1, wherein the material of said segmented rotor is
mild steel.
7. The brushless alternator of claim 1, further comprising a spacer ring on which said
rotor is mounted;
19
wherein said pair of opposed segmented discs of said rotor are axially aligned with
respect to said drive shaft; and
wherein said plurality of coils and said plurality of laminated cores are axially aligned
with respect to said drive shaft.
8. The brushless alternator of claim 7, wherein said stator further comprises a cylindrical
heat sink on which each of said stationary field coil and said plurality of coils wound on said
plurality of laminated cores are respectively mounted.
9. The brushless alternator of claim 7, further comprising a pair of stabilizer rings of
non-magnetic material, mounted one each on each of said segmented discs of said rotor at the ends
of said segments opposite said closed end.
10. The brushless alternator of claim 1, wherein said pair of opposed segmented discs of
said rotor are radially aligned with respect to said drive shaft; and
wherein said plurality of coils and said plurality of laminated cores are radially
aligned with respect to said drive shaft.
11. The brushless alternator of claim 10, wherein said stator further comprises a disc
shaped heat sink on which each of said stationary field coil and said plurality of coils wound on said
plurality of laminated cores are respectively mounted.
20
ABSTRACT OF THE DISCLOSURE:
A brushless alternator is constructed so as to have a U-shaped segmented
rotor, where each of the arms is a segmented disc, with a connecting base portion.
A stationary field coil is located at the closed end of the rotor, mounted on a heat
sink, and at the open end of the rotor there are a plurality of stator coils wound on
5 laminated cores. Each coil is wound either clockwise or counterclockwise, in
alternating fashion, and there are twice as many coils as there are segments on each
side of the rotor, for each phase of electricity that is generated. The rotor may be
arranged either axially or radially with respect to the drive shaft. Typically, the
output from the alternator is rectified.
