Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF INVENTION
FUNCq'IONALLY MODULaR BRUS~ILESS MOTOR
FIELD OF INVENTION
The present invention relates to a brushless direct
current (d.c.) motor of the type having an axial air
gap.
BACKGROUND TO ~EE INVENTION
Brushless d.c. motors of various types are known
wherein torque production is effected by the interaction
of a permanent magnet rotor and stationary winding coils g -~`
through which pulses of d.c. current pass. In the
current state of motor design, there are two seemingly -~
conflicting design goals, namely:
a) A need for a stable design and manufacturing --
situation, for economic manufacturing; and
b) A need for frequent design and manufacturing
response to rapidly changing: `~
- technology developments,
- motor application needs and possibilities
created by technology developments.
The state-of-the-art in small motor design is rapidly
changing towards motors with a number of functions ; ~`
within their enclosures and more functions than in the ~`
past. ~ m
Typical prior art structures are found in prior art ~ -
located in a search conducted in the search facilities
of the United States Patent and Trademark Office, namely
U.S. Patents Nos.:
4,5~9,902
4,326,139
4,700,943
U.S. Patent No. 4,529,902 describes a frame ;~
arrangement for a permanent magnet d.c. motor formed of
a plurality of fr~me segments which are structurally ;- ~;
modular and contain an array of permanent magnets. The
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motor is not of the brushless type, possessing a common
rotating armature for the plurality of frame segments.
U.S. Patent No. 4,326,179 describes a multipls
stator unit motor in which the s~ator comprises a stack
of a plurality of axially-spaced, circumferentially-
extending pole pieces with annular windings. An annular
armature of permanent magnets surrounds the stator
structure with pole pieces complimentary to the pole
pieces of the stator structure on its internal surface.
U.S. Patent No. 3,700,943 describes a brushless
disc-type variable reluctance motor comprising a
plurality of stator and rotor assemblies on a common
shaft.
None of this prior art is concerned with a
brushless d.c. motor of the axial gap type. As far as
the applicant is aware, there has never been a prior
proposal to provide such a motor in a functionally-
modular form. The only patent of which the applicant is
aware which makes any reference to functional modularity
is U.S. Patent No. 4,233,532. However, the motor
described in this re~erence possesses a commutator and
describes only a single functional module.
SUMMARY OF INVENTION
In accordance with the present in~ention, there is
provided a functionally modular brushless d.c. motor of
the axial air gap type. The motor combines a plurality
of individual mechanically-distinct functional modules
to provide the overall motor construction.
~ Functional modules included in the motor comprise:
(1) An electromagnetic/mechanical torque-
producing module,
(2) A shaft/bearing module, and
(3) A rotor position/velocity/acceleration sensing
module.
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The motor may optionally incorporate in the functional
modular design additional modules, including:
(4) An elactric power conditioning module,
(5) An electrical power switching module, and
~6) An information processing module.
By separating the total motor function into discrate
electrical or electromechanical functions, each of which
is embodied in a separate physical module in the total
motor assembly, very flexible design responses can be
made to a variety of application needs in conjunction
with minimal changes in manufacturing tooling and
methods. In addition, within each functional module, a
wide range of functional performance can be accommodated
with minimal effects on the other functional modules.
The motor of the present invention is significantly
different from previously-described motors in providing
functional modularity, whereas prior-described modular
motors employed structural modules and were mainly
limited to simply providing an adjustable torque
function.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a cross-sectional view of a
functionally modular brushless motor provided in
accordance with one embodiment of the invention;
Figure 2 is an exploded view of the embodiment of
Figure l;
Figure 3 is a cross-sectional view of a multiple
torque module brushless motor provided in accordance
~ with a second embodiment of the invention;
Figure 4 contains views of the shape of a stator
winding coil as used in the motors of Figures 1 to 3;
Figure 5 shows an assembly of a single set of wire
coils into a stator for use in the motors of Figures 1
to 3;
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Figure 6 contains views of a two-set winding of
wire coils for two-phase operation in the motors of
Figures 1 to 3; . .
Figure 7 is a sectional view of the functionally
modular motor of Figure 1, with a power conditioning
module adcled to the motor in a terminal box;
Figure 8 is a longitudinal sectional view of a
fluid pump assembly providedL in accordance with another
embodiment of the invention; ~.
Figure 9 is an enlarged view of Figure 1 showing
fluid flow through the fluid pump assembly;
Figure 10 contains two views of a completely
assembled rotor suitable for inclusion in the fluid pump
assembly of Figures 8 and 9, namely a plan view of the
lower face of the rotor (the upper face is equivalent)
and a sectional view alcng line A-A of the plan view;
Figure 11 contains three more-detailed views of the
lower rotor portion of the rotor assembly of Figure 10,
containing, at the top, a plan view from above of the
rotor portion, at the bottom, a plan view from below of
the rotor portion and, in the middle, a sectional view
taken on line A-A of the top plan view;
Figure 12 contains two more-detailed views of the
upper rotor portion of the rotor assembly of Figure 1,
namely a top plan view of the rotor portion and a
sectional view taken on line A-A of the top plan view; :
Figure 13 contains a perspective and sectional view . ~
of a winding assembly suitable for use in the fluid pump ~ ~;
assembly of Figures 8 and 9; and
Figure 14 contains views of the winding
construction.
GENERAL DESCRIPTION OF INVENTION ~-:
The present invention relates to a functionally
modular d.c. electric motor of the axial gap type. The
torque-producing module is one of the functional modules
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of the motor and includes electromagnetic and mechanical
elements. The torque module generally comprises a dual~
disc permanent magnet rotor and a free-standing resin-
encapsulated stator winding in the air gap between the
two rotor discs. one combined rotor and stator forms a
torque module, such that motors can be constructed
having one, two or more torque modules in tandem on a
common shaft and in a common housing.
A shaft and bearing module of desired construction
is present in the motor to support the rotor and to
provide a torque output from the motor.
A rotor parameter sensing module is provided in the
motor to determine a desired parameter of the motor for
motor control. The parameter sensed may be rotor
position, rotor velocity and/or rotor acceleration.
The sensed parameter is transmitted to an
information processing module, which may be a part of
the modular motor or may be an external device,
including a computer device. An advantage of having at
least part of the information processing module forming
a module of the modular motor is that radio frequency
interference of information signals to an external
device is avoided.
Electric control modules in the form of an electric
power conditioning module and an electrical power
switching module may be provided as part of the motor or
an external device connected to the motor.
The provision of a motor constructed of functional
modules provides a solution to the present state of
motor design technology and the presence of the
otherwise conflicting design goals mentioned above,
namely~
(a~ A need for a stable design and manufacturing
situation, for economic manufacturing; and
(b) A need for frequent design and manufacturing
response to rapidly changing:
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technology development
- motor application needs and possibilities
created by technology developments.
The novel modular motor com]bines manufacturing economy
with the ability to produce a variety of ratings from
standardized modules.
To achieve minimal interactive effects between
design changes in one functional module and the design
of other modules, special attention is paid to the
interfaces between modules in the motor. The interfaces
generally are of two kinds, namely:
(i) The physical interfaces which permit the
physical modules to be assembled into a
complete motor, and
(ii) The functional interfaces between physical
modules which permit the several functions to
cooperate in a total motor performance.
For a stable manufacturing environment, the physical
interfaces are designed to be stable even though the
scope of a functional module can vary over a
considerable range. This result is made possible by
recognizing that, in many cases, the variation in
performance interaction between modules is a flow of
information, usually in electronic form. The physical
provision for this information flow can be a stable
design configuration, even when the information flowing
is widely variable.
The interfaces between the functional modules
generally tend to be an interface with mechanical
i requirements only, an interface with both mechanical ahd
electrical requirements and an interface with only
electrical requirements. In the case of the first two
interfaces, the interface must be located within the
motor assem~ly, so that the mechanical interactions at
the interface can be accommodated. An example is the
operating interface between parts of the rotor parameter
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sensing module and between the sensing module and the
torque-producing module, in which there is a mechanical
relationship and alignment involved.
An interface of the third kind, with only
electrical requirements, provides more options as to
where related functional modules are physically located.
In this case, as noted above, some functional modules
may be located apart from the motor assembly and
enclosing housing or they may be within the motor
enclosure. An example of this kind of interface is the
interface between the power conditioning module and the
torque-producing module.
A combination of a stable manufacturing situation
and a flexible response to changing technology in each
of the above functional areas can be realized `
economically when the functions are segregated within
the motor construction, so that each function can be
dealt with separately from the others in the design and
construction of the motor. This segregation is the
basis of the modular motor of the present invention.
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DESCRIPTION OF_PREFERRED EMBODIMENTS
Referring to the drawings, there is shown in
Figures 1 and 2 one modular motor assembly in accordance
with one embodiment of the invention. In this module,
the functional segregation is taken to the point where
magnetic and electrical winding functions are in -
physically distinct components.
Figure 3 illustrates a second embodiment with four
torque modules, for an application requiring a two~
horsepower output in a small diameter frame. The motor
of Figure 3 has a shaft/bearing system which differs ~ ~ -
from that in Figures 1 and 2, and is an example of the
design flexib:ility inherent in the modular motor `
design. ,.
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In addition, the motor of Figure 1 is designed for
no internal ventilation, and to be cooled entirely by
thermal conduction to the outside surfaces of its
enclosure. In contrast, the motor of Figure 3 is a
submersible pump motor, sealed and filled with oil to
keep out the water in which it is immersed. In this
case, circulation of the internal oil adds to the
inherent conduction cooling in thermal trans~er of heat
loss to the outer surfaces of the enclosure. This is
another example of the design flexibility.
For a detailed description of the modular motor
design of Figure 1, reference is made to the exploded
view of Figure 2. In this Figure 2, part 1 is an outer
rotor disc lA with permanent magnet poles lB attached.
The poles lB may be simply attached to the steel disc
lA by a resin adhesive, such as an epoxy, or
alternatively by bolts lC or rivets located between
poles lB may be added to the adhesive, as shown in the
Figures, Eor situations of severe vibration or shock
stresses. This outer rotor lA has a shaft extension lD
shrink-fitted into its hub lE, as in Figures 1 and 2.
In that case, the axle/bearing rotor support system
described below is used, or a shaft/bearing system as
employed in Figure 3 can be used. In either case, the
bearings aan be ball bearings, or sintered bronæe
bearings, or a combination of them. By comparing
Figures 2 and 3, it can be seen that these
shaft/bearing variations leave the rotor disc modules
with only minor machining differences.
Part 3 in Figure 2 is the inner rotor disc
assembly, with permanent magnet poles 2A, which are
duplicates of those on the outer rotor 1, mounted on the
steel disc 2B. When parts 1 and 3 come together at the
motor assembly, the poles are arranged so that a pole lB
on part 1 ancl a pole 2A immediately opposite on part 3
both create a magnetomotive force across the air gap
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between them in the same axial direction. It is noted
that the complete magnetic circuit in this module
consists of only the permanent magnets and the rotor
discs. Substitution of different permanent magnet
materials, such as ferrite, cobalt-rare-earth, or
neodymium-iron, one for another, involves little or no
change in the rest of the magnet module or in other
functional modules.
The stator and winding module, part 2 in Figure 2,
comprises winding 3A, which may be encapsulated in a
fibre-reinforced resin material ~n a mould, and a pre-
machined metal housing 3B, as in Figure 2.
Alternatively, as in Figure 3, the encapsulating of the
winding may form the entire winding and housing
structure of a stator module.
The winding 3A is designed for automated
production. Coils in the stator module 2 are wound on a
stationary form, with offset end-heads, as shown in
Figure 4. A set of coils (e.g. for an 8-pole motor, as
in Figure 5) is wound with continuous wires by indexing
a carrier disc between the winding of individual coils.
Such a set of coils is shown in Figure 5. The coils may
be held in place for removal from the carrier by tape
ties, as in Figure 5, or by alternative means, such as
spots of hot-melt adhesive. The motors are usually
designed for two-phase operation.
The two-phase operation winding is produced by
assembling two coil sets with their offset end-heads on
opposite sides of the disc formed by their radial
portions which lie in a common plane, as in Figure 6.
This is a complete winding. For handling be~ore
moulding, it is temporarily integrated by tape ties, or
spot~adhesive means, or cemented to a thin insulating
lamination disc which later becomes part of the
encapsulated structure. This winding is wound with two
strands of enamel insulated wire in parallel, each
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strand becoming a separate winding for the control
system. The assembled winding is placed in a metal
mould, along with glass fibre cloth pieces to reinforce
the sur~aces of the winding when 0ncapsulated. The
mould then is filled with a suitable resin material,
either thermosetting or thermoplastic, to produce a
stator module 2 with precise dimensions.
The outer rotor 1 and inner rotor 3 are assembled
together using bolts lF or other convenient means with
the hub 2C of the inner rotor 3 passing through an axial
opening 3C in the winding 2 so that the outer rotor 1,
inner rotor 3 and winding 2 provide a torque-producing
module.
Part 4 in Figure 2 is an annular rotor position
information disc. The disc 4 may be a plastic laminate
or metal clisc, depending upon the pattern required to be
carried and the kind of sensing devices which read the
information from the disc. One face 4A of the disc 4 is
simply used to mount it on the inner rotor module, part
3, with an adhesive. On the other face 4B is an
information pattern which can take one of several forms,
namely:
- A black and white reflective pattern produced
by photographic means or printing, and used
with reflective optical electronic sensors, or
- A shaped contour in a metal disc, produced by
machining or stamping, and used with Hall-
effect sensors and small magnets, or with
other kinds of proximity sensors.
The complexity of the information pattern on the disc 4
can vary from very simple, such as location of rotor
pole edges only, to very complex, including precise
rotor positions in degrees of displacement from a zero
reference point on the rotor. The resolution possible
is quite h:igh because the disc face 4B has a diameter
essentially equal to the rotor diameter.
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Part 7 in Figure 2 is a module containing from two
to four sensors which read the information pattern from
the information disc, part 4, and transmit it to a
control logic module, part 9. The sensor module 7 and
5the information disc 4 comprise a rotor parameter
sensing module. The number of sensors used, their
relative locations, and their type, depends on the co-
ordinated design of the rotor information system. The
sensors are carried in a standardized mounting module so
10that a variety of systems can be interchanged in an
otherwise unchanged manufacturing situation.
Part 6 in Figure 2 is an electronic power switch
mounting disc, and in Figures 1 and 2, also constitutes
the axle support disc for an axle and bearing module,
15item 5. In the Figure 3 motor, part 6 is a bearing
support disc. Part 6 has both mechanical and thermal
functions, since the disc mechanically supports a rotor
axle or shaft and also acts as a heat-sink, thermally
conducting path for cooling the power switches, part 8.
20The axle and bearing module 5 including a
stakionary hub member 5A which is mounted to the axle
support 6 by bolts 5B. The stationary hub member
supports two bearing cases 5C and 5D which mount the
inner and outer disc 3 and 1 respectively in rotational
25relationship with the hub 5A.
The axle and bearing module 5 may be provided with
an axial bore. By varying the ratio of the inner rotor
pole radius to the outer pole radius, the bore may be
made as large as desired, to an extreme of a motor which
30; is essentially an annular rotor pole ring surrounding a
circular cylinder. In this case, the rotor and the
stator may be in the form of bipolar or multi-polar
segments. It i also possible to use fewer of the
modular segments than in a complete ring.
35Part 9 in Figure Z is an electronic-logic printed
circuit board which controls the operation of the motor
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by periodically turning on the power switches to various
windings for pulses of electric current, and may contain
analog or digital logic devices, or a combination of
them. The circuit board 9 comprises an information
processing module.
The logic also can vary from very simple logic to
very complex information processing, including the use
of microprocessor systems and devices. This complex
level of information processing can include adjusting
the motor performance parameters, such as a RPM, torque,
acceleration, etc., in automatic response to conditions
sensed in the environment or in a driven device.
When two or more torque modules are employed, for
example, as in Figure 3, the total torque of the motor
can be made somewhat smoother by displacing aach torque
module circumferentially with respect to the other~s) by
a fraction of a pole pitch. For example, with a two
torque module motor, the displacement of one module with
r~spect to the other may be l/4 of a pole pitch when
each module has a two-phase stator winding. This
arrangement overlaps the torque pulses from one module
with the torque pulses from the other, thereby providing
a smoother overall torque output. This improvement in
performance is obtained at no appreciable additional
cost, although an additional rotor position sensor is
required.
In addition, when two or more torque-producing
modules are employed, it is not necessary that they have
the same torque rating. One or more may differ from the -
others ~in torque rating as well as associated axial
dimensions. Radial dimensions would remain similar so
as to obtain a common fit on a common shaft and a common
fit in a common housing. Thé advantage of this
arrangement is the capability of varying the torque
increments as modules are added to the motor and the
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choice of different torque steps available from modules
of different torque rating.
In Figure 7, there is item 11 added to the modular
motor assembly in the form of a power conditioning
module in a terminal box mounted to the motor.
The embodiment of Figure 7 also differs from that
shown in Figure 1 by providing a bracket 12 at the shaft
end of the motor by which the motor may be flange
mounted f~r attachment to a driven machine. Fan blades
13 are attached to the outer rotor disc 1 to provide air
flow over the frame of the motor to cool it.
Turning now to Figures 8 and 9, there is
illustrated therein another embodiment of modular motor
provided in accordance with the invention. Figure 8 is
a longitudinal sectional view of a complete electronic
controlled, electromagnetically driven, fluid pump
assembly 100. Each major element in the assembly 100 is
essentially circular or disc shaped and fits into a
cylindrical enclosing caRe 11, which can be of thin
metal as shown in Figure 8, or other material, such as
molded plastic. The metal case 11 is flanged inwards at
both ends to make the assembly fluid-tight at resilient
"O" ringS 21, 31
Part 41 is an electronic control component for the
pump 100, the electronic elements being encapsulated in
a resin material suited to chemically resist attack by
the fluid being pumped through the assembly 100.
Part 51 is a winding capable of producing a
magnetic field when a d.c. electric current is passed
therethrough, encapsulated in a resin material suited to
chemically resist attack by the fluid being pumped
through the assembly 100.
Part 61 is a permanent magnet rotor assembly which,
together with the winding 51, whan energized, provides
torgue to drive the pump 100. The permanent magnet
rotor assembly consists of magnet poles 71, attached to
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two steel discs 81, which are integrated into an
assembly by a moulded metal or resin hub 9l.
The rotor hub 9l has projecting prongs 102 on its
lower end which engage and drive gear-pump elements lol
and 1l1. These pump elements are located for rotation
on a stationary axle 121 and in a stationary annular
housing 131. This housing, in turn, is attached by
screws 141 to a pump inlet assembly 151. ~esin-laminate
washers 161 and 171 complete the enclosure for the pump
elements.
The pump elements 111 and 121 in the illustrated
embodiment provide a rotary, positive displacement, type
pump. When driven at constant speed (RPM), the pump
delivers a constant quantity of pumped fluid, developing
the pressure required to cause that quantity to flow in
the discharge system. A spring-loaded, pressure-relief
ball valve 181 is set to prevent excessive pressure
being developed.
The working fluid from the pump elements 111 and
12l ~lows through passaqes in the enclosure to leave the
pump at an outlet pipe 191. The flow path of fluid
through the pump 100 is shown in the enlarged view of
Figure 9 and is described in detail below. Since the
system being supplied by the pumped fluid is under
pressure, a ball check-valve 201 is usually used. The
pump 100 is intended to operate wholly or partly
submerged in the fluid being pumped. In the illustrated
embodiment, a vapour-venting ball valve 211 is included
for the partly submerged situation.
Electric power enters the pump enclosure at
terminals 221 which connect internally to the electronic
controls 41 and from there to the motor windings.
Two annular moulded or cast resin motor housings
241 and 251 surround the motor rotor assembly 61 and
clamp the encapsulated winding disc 51 between their
inner flange edges. The inner cavities in these housing
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parts are shaped to a clearance at the rotor periphery,
and in conjunction with an accurately dimensioned
winding disc, to provide close toleranced small axial
clearances between the axial faces of the rotor disc 81
and the inner housing faces 104. There are also close
toleranced small axial clearances between the rotor air-
gap pole faces 106 and the l`aces of the winding disc 51.
Fluid flow channels are provided on the outer
periphery of the motor housings 241 and 251. One
channel 26~ conducts fluid from the pump inlet and
delivers approximately one half of it to the upper
housing 241 and the other half to the lower housing,
251. .
In the openings which connect fluid channel 261 to
the inner housing cavities 108 and 110 of the housings
241 and 251 are located orifice discs 271 which regulate -~
and balance the fluid flows to the two housings.
From the two inner housing cavities 108 and 110,
the Pluid flows radially outward through the clearances
112 and 114 between the housing and rotor disc faces. A
small fraction of the fluid from the housing recesses
passes through small axial openings 281 in the rotor
hub, to the clearances 116 and 118 between the rotor
pole faces and the winding disc faces. This fluid flows
radially outward to the rotor periphery cavity where all
four flows re-combine at the motor fluid outlet 291.
A central opening 120 in rotor hub 19l locates the ~-
rotor radially on a projection of the pump axle 121.
From the motor housing, fluid outlet 291 and channels
301 are provided on the outer periphery of the upper
motor housing 241, which carry the fluid to the pump
assembly outlet tube 191.
In operation of the pump 100, the close clearance
gaps 112, 114, 116 and 118 in the arrangement are
proportioned so that the inner gaps 116 and 118 between
rotor pole faces 71 and winding disc faces 51 are larger
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than the outer clearances 112 and 114 between the rotor
disc faces 81 and the housing faces 241 and 251. When
the pump 100 is de-energized and stopped, the internal
cavities of the assembly may more or less drain back
through the pump into the fluid tank in which the pump
assembly is more or less immersed, depending on how deep
the fluid is in the tank. If the assembly cavities are
drained, the rotor 61 settles down to rest on the lower
housing with disc face 81 on the housing face 251.
Capillary action may retain some fluid in this contact
area, but the design does not rely on it. The nature of
the housing material and the rotor disc face, and the
surface finishes, are selected for low friction when the
contact area is dry.
When the pump 100 is energized electrically, a few
revolutions begins to force fluid into the enclosure,
soon filling the enclosure completely, closing the vent
valve 211 and starting to build up pressure and fluid
flow. As fluid flow through the pump enclosure builds
up, there is quickly established a balanced, opposing,
hydrostatic thxust bearing effect at the clearances 112
and 114 batween the motor housing faces and the rotor
disc outer faces. With suitably chosen clearance gaps
and fluid flows, these thrust bearing films are
dynamically "stiff"; i.e. relatively large changes in
thrust force produce correspondingly small changes in
the gap height. For instance, in the illustrated pump
design, a doubling of the thrust force only changes the
gap clearance from 0.005 inches to 0.004 inches. The
motor rotor effectively floats on fluid films which are
independent of motor speed and depend only of the fluid
flow rate.
In the rotor to winding disc clearances 116 and
118, the fluid flows are intended chiefly to remove
resistance loss heat from the winding disc 51.
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In the clearance gaps 116 and 118, the axial
clearances are large enough that the hydrostatic thrust
effect is small. The fluid flow through these
clearances is determined by the sizing of the small
holes in the rotor hub 281.
The fluid pressure drop in this bearing system is a
small fraction of the pump delivery pressure. For
instance, in one case studied, the pressure drop was
calculatesl at less then 1 PSI (lb./sq.in.) with a pump
delivery pressure of 45 PSI.
Referring now the Figures lO to 12 of the drawings,
a rotor assembly 200 is built up by first attaching four
permanent magnet poles 202 to a steel disc 20~, using a
resin adhesive or other suitable means. The poles may
be premagnetized or magnetized later. Since axial
dimensions in the assembly are to close tolerances, the
disc and magnet assembly may be surface ground to a
toleranced thickness. A pre-machined hub 203 of
suitable plastic or metal also carries five projec:ting
pins 206, which transmit the torque developed in the
rotor 200 to the gear-pump elements 101 and 111 in the
assembly of Figures 8 and 9 described above.
Suitability of the hub material is in terms of its
function as a bearing material, as described below. A
tapped thread 207 in an axial opening 207A in the hub is
optional, as explained later. The disc and magnet
assembly 201 and 202 and the hub, then are positioned in
a mould and a resin or low-melting temperature metal is
injected to form a matrix 204, filling the spaces, as
shown in Figure 11. A triangular notch 208 in the top
end of the hub 203 is oriented to a specific location
during this moulding operation, relative to a specific
polarity of magnet poles 202. This notch 208 is
important for later assambly of the complete rotor.
After the moulding operation, a small capillary sized
hole, 205, is drilled through the matrix 204. The
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provision of the capillary opening 205 as a post-
moulding operation is necessary, since the opening 205
is too small to be included in the moulding operation.
The mould tool ensures required close toleranced
dimensions in the assembled rotor.
Referring now to Figure 12, thera is shown therein
details of the upper rotor. A steel disc 211 and
magnets 212 in this rotor are identical to the disc and
magnets in the lower rotor (Figure 11) and are similarly
assembled and processed, but no pre-machined hub is used
in this rotor, in contrast to the lower rotor portion
shown in Figure 11. The disc and magnet assembly, pre-
machined if necessary, is put into a moulding fixture
and the matrix material 213 is injected to fill the
spaces detailed in the drawing. Included in this
mouldiny is a triangular key or tongue 214 shaped to
match the notch 208 in the hub 203 of the lower rotor,
and again oriented during the moulding operation to a
specific polarity of magnet pole. In this case also,
the mould tool ensures the required close-toleranced
dimensions in the moulded rotor.
Upper and lower rotors shown in Figures 11 and 12,
are assembled into a dual-disc rotor as seen in Figure
10, during final assembly of the complete fluid/pump
unit 100 shown in Figures 8 and 9 and forms part of the
torque-producing module in the functionally modular
construction of Figures 8 and 9. As thus assembled, the
upper and lower rotors are held together by the strong
magnetic attraction between the two sets of permanent
magnet poles 202 and 212, these poles being aligned by
the engagement of the key 214 in the upper rotor and the
slot 208 in the hub 203 of the lower rotor. For most
applications, this magnetic force is more than adequate
to ensure that the dual-disc rotor acts as a single
unit, even with usual external vibrations or shock
loading from the working environment. For example, in
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the rotor depicted in Figure lo, the weight of an upper
rotor of 1.5 inches outer diameter may be about 3
ounces, while the magnetic: restraining force may be
about 8 pounds, or 128 ounces. Therefore, it would
require a vertical acceleration of 128/3, or ~2 G, (42
times the acceleration due to gravity) to cause the
upper rotor to begin to move off its seating on the
lower rotor.
In the remote event that more restraining than
provided by the magnetism is desired, a screw 231 can be
added passing through the axial opening 213A in the hub
213 and into engagement with the screw thereto 207 in
the hub 203. In a small rotor, the screw 231 would be
omitted, to save costs.
Turning now to Figures 13 and 14, there is
illustrated therein a winding assembly useful for
inclusion in the fluid pump motor of Figures 8 and 9 and
for combination with the rotor unit illustrated in
Figures 10 to 12 to provide a torque-producing module
for a funationally-modular d.c. motor.
The upper view in Figure 13 is an isometric view of
a completed disc winding 300, with the same disc winding
being shown in section in the lower part of the drawing.
This winding 300 has four poles, magnetically. The
winding begins as four coils 310, as shown in Figure
14A, each of which may contain, for example, 25 turns of
# 28 AWG enamelled wire 301, wound two wires in
parallel. For simple manufacturing, these coils begin
as a single coil of 100 turns (Figure 14B), which then
is divided into four bundles of 25 turns (Figure 14A).
Alternate bundles are turned over and spread into a
circle to Eorm four interconnected coils 310 of
alternating polarity, shown as in Figure 14C. There
are four terminal wires 312 for the set of coils, namely
a start and finish lead for each of the two parallel
wires, which are used as two separate windings in the
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motor operation. To facil:itate handling of the set of
coils, they are spot-cemented to a thin resin laminate
disc 304.
Part 303 of Figure 13 is an assembly of connecting
pins and a rotor position sensor 305 which forms part of
the winding assembly 300. The rotor position sensor 305
provides another functional module of the pump assembly
100. The assembly 303 includes four winding connecting
pins 314, and three pins 316 for the sensor connections
to the controls. The assembly 303 may be pre-moulded
and then incorporated into the final moulding of the
winding. All moulding of the winding construction is in
a resin which is chemically inert to the fluid being
pumped in the fluid pump 100 and which surrounds the
winding in the fluid pump 100 as described above. For
the simple controls of the pump motor 100, a single
Hall-effect sensor 305 may be used to sense the rotor
position when the rotor is stationary as well as when it
is moving. The location of this sensor 305 and of the
connecting pins 316 needs to be quite precise and the
precise locations are achieved hy pre-mould tooling, if
used, and by the final moulding of the winding assembly
with resin.
Also included in the winding assembly 300 are
pieces of magnetically soft ferrite 307 and 308. These
soft ferrite pieces 307 and 308 are shaped and located
within some of the winding coil areas to ensure that the
rotor poles 71 always come to rest, when the pump 100 is
stopped, in a position relative to the winding coils 310
~ I such that, when the pump 100 is again energized, the
first pulse of current in a winding coil 310 produces a
positive torque on the rotor in the pre-determined
direction of rotation. At the same time, the shapes,
locations, and amounts of these soft ferrite pieces 307
and 308 are limited so that their torque effect when the
motor is running is acaeptably small. This feature of
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21
the winding construction makes it possible to use
simple, single-phase electronic controls. The ferrite
pieces may be spot-cemented to the resin laminate disc
304 carrying the winding coils before ~inal
encapsulation.
The assembly then is put into a mould which
accurately positions each element to its required
relative location, and the resin is injected to ~ill the
mould and produce the desired final shape and dimensions
o~ the winding shown as 51 in Figure 8. The moulding
operation provides:
1. Smooth and even upper and lower disc surfaces,
accurately spaced apart to a small tolerance (e.g.
0.002 inch);
2. Accurate locating of the connecting pins 303
both radially and circumferentially, relative to
the winding coils 310;
3. Accurate locating of the rotor position sensor
305, both radially and circumferentially, relative
to the winding coils 310; and
4. Semi-precise location of the coil sides and
~errite pieces.
On the periphery of the finished winding 300 are
provided two notches 309, which provide channels for
axial flow of fluid in the fluid pump 100.
The moulded winding assembly 300, produced as
described above with respect to Figures 13 and 14, has
~our main operating functions in the pump assembly 100,
namely:
1. In cooperation with the permanent magnet rotor
200, the winding assembly 300 produces torque to
drive ~luid pumping elements;
2. The winding assembly provides a rotor position
signal to the electronic controls, when the pump is
running and when it is stopped;
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22
3. The winding assembly combines with other pump ;~
elements to provide close-toleranced paths for
fluid flow through the pump assembly 100; and `
4. The controlled fluid flow through small
clearances between the outer faces of the ---~
encapsulated winding and the rotor pole faces
provides a very effective liquid cooling of winding
resiætance losses. ~ `~
SUMMARY OF DISCLOSURE
In summary of this disclosure, the present
invention provides a novel direct current motor assembly
by providing the motor in functionally modular form.
The present invention also provides specific
arrangements of functional modules in specific motor
assemblies and specific rotor and stator elements to
provide torque-producing modules in such pump
assemblies. Modifications are possible within the scope
of this invention.
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