CA2005807A1 - Functionally modular brushless motor - Google Patents
Functionally modular brushless motorInfo
- Publication number
- CA2005807A1 CA2005807A1 CA 2005807 CA2005807A CA2005807A1 CA 2005807 A1 CA2005807 A1 CA 2005807A1 CA 2005807 CA2005807 CA 2005807 CA 2005807 A CA2005807 A CA 2005807A CA 2005807 A1 CA2005807 A1 CA 2005807A1
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- Canada
- Prior art keywords
- rotor
- motor
- winding
- disc
- module
- Prior art date
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Abstract
ABSTRACT OF THE DISCLOSURE
A construction for an axial air gap, functionally modular brushless D.C. motor is described. The total motor function is separated into certain discrete electrical or electromechanical functions, each of which is embodied in a separate physical module in the total motor assembly. The separation of the functional entities permits a very flexible design response to a variety of application needs in conjunction with minimal changes in manufacturing tooling and methods.
A construction for an axial air gap, functionally modular brushless D.C. motor is described. The total motor function is separated into certain discrete electrical or electromechanical functions, each of which is embodied in a separate physical module in the total motor assembly. The separation of the functional entities permits a very flexible design response to a variety of application needs in conjunction with minimal changes in manufacturing tooling and methods.
Description
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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 '"~ -: ~. '-' `` 2~058~7 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:
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 '"~ -: ~. '-' `` 2~058~7 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 ~05~
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:
2~5~ 7 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.
':, 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 `
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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 Z~8~7 ~:
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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 2~ 7 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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)58~ 7 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 05~
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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 ' ' :- 2~)05~3~7 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 '..-'';'' ~'''.' :, ;..: :
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 .
--` 2~)5~3~37 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 ~ ' 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 : . :- . , ~, , , ,,: ,.. .. .
~ 5~3~'7 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 ' ''' ' ~ '',' :-` 2~05i8~3'7 , 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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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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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 ~05~
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:
2~5~ 7 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.
':, 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 `
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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 Z~8~7 ~:
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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 2~ 7 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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)58~ 7 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 05~
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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 ' ' :- 2~)05~3~7 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 '..-'';'' ~'''.' :, ;..: :
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 .
--` 2~)5~3~37 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 ~ ' 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 : . :- . , ~, , , ,,: ,.. .. .
~ 5~3~'7 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 ' ''' ' ~ '',' :-` 2~05i8~3'7 , 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;
- 2~)~58~
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.
.: ~ ,.
~ , , .
Claims (23)
1. A functionally-modular brushless d.c. motor of the axial air axial gap type.
2. The motor of claim 1 comprising:
(a) a torque-producing module, (b) a shaft and bearing module, and (c) a rotor parameter-sensing module.
(a) a torque-producing module, (b) a shaft and bearing module, and (c) a rotor parameter-sensing module.
3. The motor of claim 2, wherein said torque-producing module comprises a dual-disc permanent magnet rotor defining an air gap therebetween and a free-standing stator winding in the air gap between the rotor disks.
4. The motor of claim 2, wherein the rotor parameter-sensing module includes means for sensing rotor position, rotor velocity or rotor acceleration.
5. The motor of claim 2 further comprising at least one additional module interfacing electrically and/or electromagnetically with the motor.
6. A brushless d.c. motor which is constructed from mechanically distinct functional modules, each of which is essentially disc shaped, and wherein the total motor is assembled as an axial arrangement of functional modules.
7. The motor of claim 6, wherein an electromagnetic/mechanical torque module consists of two rotor discs each carrying permanent magnet poles and a free-standing encapsulated, disc-shaped, stator winding located in an axial air gap between the poles of the rotor discs.
8. The motor of claim 7, wherein more than one torque module is combined with one each of the other functional modules to produce a complete motor.
9. The motor of claim 7 wherein the encapsulated winding has soft ferrite or permanent magnet ferrite included in the structure in parts of the stator disc portion not occupied by windings to provide for a controlled stop position of rotor magnets relative to the stator winding.
10. The motor of claim 6 wherein the windings in one or more torque modules are switched by electronic control between series and parallel connections to operate from different voltages or at different inherent speeds from the same supplied voltage.
11. A brushless d.c. fluid pump wherein the pumped fluid flows through a pump enclosure, which comprises a disc-shaped motor winding located in an axial air gap between two sets of permanent magnet poles arranged in a disc-shaped rotor assembly to provide a torque-producing module of said pump wherein two opposing hydrostatic thrust bearings for the rotor are provided such that, when pumped fluid flows under pressure through the pump enclosure, the rotor assembly floats stably on fluid films.
12. The fluid pump claimed in claim 11, wherein with the fluid flow through the pump is divided between the two thrust bearings by means of controlled dimension orifices provided in series with respect to fluid flow for fluid flow to each bearing.
13. The fluid pump claimed in claim 11, wherein said disc-shaped rotor assembly comprises a hub having capillary sized openings therein to control fluid flow to axial clearance gaps between the winding and permanent magnet pole faces of the rotor to cool the motor winding.
14. A rotor assembly for use with a functionally modular d.c. motor, comprising two sub-assemblies pre-formed to precise dimensions and close tolerances, from imprecise or semi-precise components by integration with a resin or metal matrix in a precision mould.
15. The rotor assembly of claim 14 wherein the two sub-assemblies are held together in a final assembly by magnetic forces between permanent magnet poles facing each other across an axial air gap.
16. The rotor of claim 15, wherein mechanical means to hold the two sub-assemblies together is added to the magnetic holding force.
17. A disc-shaped winding for location in an axial air gap between two sets of permanent magnet poles to provide a torque-producing module, which is moulded to a precise shape and dimensions in a resin material.
18. The windings of claim 17, wherein a set of multipolar coils is formed by winding as a single coil, and separating the turns into bundles each forming one pole in a set of coils already interconnected.
19. The windings of claim 18, wherein the winding coils terminate in rigid pin-type connectors, precisely located during a winding moulding operation so that the winding can be made and assembled into a motor and pump assembly by automated or mechanized processes.
20. The windings of claim 18, wherein a precisely located rotor position sensor is included in the winding structure.
21. The windings of claim 18, wherein the coils are wound with two conductors in parallel which are connected to the power supply as two separate windings of opposite polarities, and an associated electronic control system with a minimum of power switches.
22. The windings of claim 21, wherein each conductor consists of two or more strands of insulated fine copper wire, to reduce eddy currents in the conductors which result from their location in a moving magnetic field.
23. The windings of claim 21, wherein embedded in the winding structure are shaped and sized pieces of magnetically soft ferrite material so located as to determine that the permanent magnet rotor used with the winding will always come to rest in a particular location relative to the winding poles, to produce positive starting torque in a predetermined direction of rotation, with single-phase electronic controls.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US376,628 | 1982-05-10 | ||
| US37662889A | 1989-07-07 | 1989-07-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2005807A1 true CA2005807A1 (en) | 1991-01-07 |
Family
ID=23485802
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2005807 Abandoned CA2005807A1 (en) | 1989-07-07 | 1989-12-18 | Functionally modular brushless motor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2005807A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5767600A (en) * | 1997-02-27 | 1998-06-16 | Whiteley; Eric | Modular motor |
| WO2004057738A1 (en) * | 2002-12-20 | 2004-07-08 | Jannali Holdings Pty Ltd | Modularly segmented air core windings electric motor or generator |
| GB2450157A (en) * | 2007-06-15 | 2008-12-17 | Baker Hughes Inc | System For Monitoring An Electrical Submersible Pump |
-
1989
- 1989-12-18 CA CA 2005807 patent/CA2005807A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5767600A (en) * | 1997-02-27 | 1998-06-16 | Whiteley; Eric | Modular motor |
| WO2004057738A1 (en) * | 2002-12-20 | 2004-07-08 | Jannali Holdings Pty Ltd | Modularly segmented air core windings electric motor or generator |
| GB2450157A (en) * | 2007-06-15 | 2008-12-17 | Baker Hughes Inc | System For Monitoring An Electrical Submersible Pump |
| GB2450157B (en) * | 2007-06-15 | 2011-12-21 | Baker Hughes Inc | System for determining an initial direction of rotation of an electrical submersible pump |
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