Patent Application
20090009011
The invention relates to motors able provide high torque at low speed, and in particular to the use of radial magnetic force in such motors.
Motor-Generator machines able to provide high torque at low speed, which are compact, are disclosed in the art.
WO05112584 discloses a motor-generator machine comprising a slotless AC induction motor. The motor disclosed therein is an AC induction machine comprising an external electrical member attached to a supporting frame and an internal electrical member attached to a supporting core; one or both supports are slotless, and the electrical member attached thereto comprises a number of surface mounted conductor bars separated from one another by suitable insulation. An airgap features between the magnetic portions of core and frame. Electrical members perform the usual functions of rotor and stator but are not limited in position by the present invention to either rôle. The stator comprises at least three different electrical phases supplied with electrical power by an inverter. The rotor has a standard winding configuration, and the rotor support permits axial rotation.
WO2006/002207 discloses a motor-generator machine comprising a high phase order AC machine with short pitch winding. Disclosed therein is a high phase order alternating current rotating machine having an inverter drive that provides more than three phases of drive waveform of harmonic order H, and characterized in that the windings of the machine have a pitch of less than 180 rotational degrees. Preferably the windings are connected together in a mesh, star or delta connection. The disclosure is further directed to selection of a winding pitch that yields a different chording factor for different harmonics. The aim is to select a chording factor that is optimal for the desired harmonics.
WO2006/065988 discloses a motor-generator machine comprising stator coils wound around the inside and outside of a stator, that is, toroidally wound. The machine may be used with a dual rotor combination, so that both the inside and outside of the stator may be active. Even order drive harmonics may be used, if the pitch factor for the windings permits them. In a preferred embodiment, each of the coils is driven by a unique, dedicated drive phase. However, if a number of coils have the same phase angle as one another, and are positioned on the stator in different poles, these may alternatively be connected together to be driven by the same drive phase. In a preferred embodiment, the coils are connected to be able to operate with 2 poles, or four poles, under H=1 where H is the harmonic order of the drive waveform. The coils may be connected together in series, parallel, or anti-parallel.
U.S. Patent Appl. Pub. No. 2006/0273686 discloses a motor-generator machine comprising a polyphase electric motor which is preferably connected to drive systems via mesh connections to provide variable V/Hz ratios. The motor-generator machine disclosed therein comprises an axle; a hub rotatably mounted on said axle; an electrical induction motor comprising a rotor and a stator; and an inverter electrically connected to said stator; wherein one of said rotor or stator is attached to said hub and the other of said rotor or stator is attached to said axle. Such a machine may be located inside a vehicle drive wheel, and allows a drive motor to provide the necessary torque with reasonable system mass.
WO2006/113121 discloses a motor-generator machine comprising an induction and switched reluctance motor designed to operate as a reluctance machine at low speeds and an inductance machine at high speeds. The motor drive provides more than three different phases and is capable of synthesizing different harmonics. As an example, the motor may be wound with seven different phases, and the drive may be capable of supplying fundamental, third and fifth harmonic. The stator windings are preferably connected with a mesh connection. The system is particularly suitable for a high phase order induction machine drive systems of the type disclosed in U.S. Pat. Nos. 6,657,334 and 6,831,430. The rotor, in combination with the stator, is designed with a particular structure that reacts to a magnetic field configuration generated by one drive waveform harmonic. The reaction to this harmonic by the rotor structure produces a reluctance torque that rotates the rotor. For a different harmonic drive waveform, a different magnetic field configuration is produced, for which the rotor structure defines that substantially negligible reluctance torque is produced. However, this magnetic field configuration induces substantial rotor currents in the rotor windings, and the currents produce induction based torque to rotate the rotor. The above five patents describe motors which produce high torque as a low speed overload condition.
In a conventional electric induction motor, an alternating current induces a magnetic field in a stator, causing a rotating radial magnetic force which attracts the rotor to the stator. The rotating magnetic field in the stator induces currents in the rotor. The rotor and stator currents interact to produce a tangential magnetic field and therefore a tangential force. This tangential force is between 1 and 10% of the radial magnetic force between rotor and stator. A typical tangential force per unit area is 2 PSI. The tangential force drives the rotor. The much larger radial force is balanced by the rotational symmetry of the apparatus and therefore causes no motion. If unbalanced, the radial force would act to move the rotor towards the stator until it meets. In a non-rotationally symmetric motor, this would result in a self-destructive system. Therefore, non-rotationally symmetric motors require bearings to balance the radial force.
Note that magnetic normal force causes work to be done by way of relative motion between a magnet (or piece of ferromagnetic material such as plain steel) and a magnetic field. Once the rotor and stator are in contact, no further motion is possible and no further work is done. Further note that the strength of a magnetic force depends upon the magnetic flux density, which itself depends upon the distance between the magnetic materials, i.e. the rotor and stator in a conventional motor. Over a large airgap, a large magnetic flux density cannot be sustained, and thus the normal force is reduced.
The use of gears alongside motors is known in the art. Motors use gears to increase or decrease the output speed or torque, to alter the direction of rotation, or to link multiple elements, for example.
US2006/111214 (Yan and Wu) discloses a geared motor includes a rotor mounted rotatably to a motor housing and having an output shaft along a rotating axis, and a stator secured to the motor housing to surround the rotor. The stator has a plurality of angularly displaced core segments with wall areas confronting magnetic pole units on the rotor, and a plurality of windings wound respectively around the core segments to create a torque so as to drive the output shaft. A planetary gear assembly includes a sun wheel mounted on the output shaft, an annulus secured to the motor housing and having an internally toothed annular surface, and a planet wheel meshing with the toothed surface and the sun wheel. A rotary member is rotated by a speed reduction drive transmitted from the planet wheel about a transmitting axis aligned with the rotating axis.
GB1438555 (RCA Corp) discloses a system for rotating the antenna mast of a television set and providing a local indication of its rotated position. The system comprises a split-phase A.C. induction motor driving through a gear train the shaft of the mast and a cam controlling a changeover switch.
U.S. Pat. No. 4,122,377 to Drummond discloses a drive unit comprising two induction motors mounted side-by-side in a housing. Each induction motor has a stator element and a rotor element, which elements are suitably journaled so that both stator elements and both rotor elements are rotatable. The stator elements are mechanically linked by a gear train so that rotation of one stator element opposes rotation of the other stator element when both induction motors are energized. Therefore, the stator elements buck one another and induce torque in the rotor elements.
The article entitled Digital control and optimization of a rolling rotor switched reluctance machine, Reinert 1995, discloses a motor having a rotor which is free to roll on the inside of the stator. It uses axial tangential forces between rotor and stator, and gear teeth which are spatially distinct from the stator.
G.B. Patent No. 883884 to Rosain discloses an eccentric rotor rolling inside a stator with a complex suspension arrangement to enable the oscillating motion to be absorbed. The rotor rollers have rubber tires.
Japanese Patent No. 2006234005 to Hazama discloses a speed reducer having a rotor having a driven portion concentric with the stator, driven by tangential magnetic force, and a separate eccentric portion which rolls on the inside of the stator to produce a reduced speed.
G.B. Patent No. 2340669 to Inkster discloses a rolling rotor motor which uses radial magnetic force from sequential energization of solenoids around a stator to cause motion of the rotor. The rotor is constrained into a circular region by transfer means or a flexible coupling and held in a circular path by the same radial magnetic force which causes the motion.
U.S. Pat. No. 3,770,997 to Presley discloses a rotory actuator which has a rotor constrained to orbit an eccentric by magnetic forces. Presley uses magnetic ring elements to create ‘hold-in force’. The ring elements contact the rotor at the point where it contacts the stator, which extra mechanical contact is a disadvantage since it will cause friction and wear and tear.
U.S. Pat. No. 2,857,536 to Light discloses a variable reluctance machine with an eccentric shaft and hypocycloidal gearing. Light depends upon magnetic forces to constrain the rotor to wobbling, thus using magnetic force to overcome gear separation forces.
U.S. Pat. No. 2,561,890 to Stoddard discloses a ‘Dynamoelectric machine’ wherein an eccentric rotor is pulled around directly by magnetic flux, for the purpose of operating as a pump. The rotor (movable member 11) is axially displaced from the stator (stationary member 10 having chamber 10a formed by cylindrical brass sleeve 12) with sleeve 12 extending axially from inside stator 10, to form a chamber 10a, part of which is axially displaced from stator 10.
It can be seen from the forgoing that it would be advantageous to harness the strong radial magnetic force present in the steel core of conventional induction motors, and use it to drive an induction motor, instead of using the smaller tangential force produced in the windings. This is an object of the present invention.
It would be further advantageous to do so without creating unbalanced forces which require bearings to prevent the motor from becoming unbalanced. This is a further object of the present invention.
It would be further advantageous to have an induction motor using gears to modify the speed of rotation, wherein the contact forces and/or speed of rotation of said gears are low, in order to reduce wear and tear of the gear teeth. This is a yet further object of the present invention.
Disclosed is an electric motor and hypocyclic gearing system, wherein magnetic forces are used to directly drive the eccentric or wobbling gear element. In prior art, hypocyclic gearing systems are well known. In such systems, the high-speed input rotates at high speed, driving an eccentric element. This eccentric element further drives a wobbling geared element, which meshes with a stationary gear. The wobbling geared element is thus forced to oscillate or wobble at high speed, while rotating at low speed.
In the method of the present invention, the high speed input and eccentric conversion device is eliminated. Instead the wobbling geared element is directly driven by magnetic forces. Eccentric bearing elements are removed from the system, and stresses associated with high-speed operation of the motor are reduced. Owing to the much greater magnetic force in the normal rather than shear direction, torque density of the motor itself is substantially increased.
A motor is disclosed, comprising at least one fixed member comprising at least one magnetic winding, having an internal cavity; at least one driven member inside said fixed member, comprising magnetically conductive materials; constraining means for constraining said driven member to a path of movement with respect to said fixed member, said driven member being able to move within said fixed member, wherein magnetic normal force is induced in said fixed member periodically, whereby said driven member is periodically moved around said path by magnetic force, whereby rotary motion is produced.
The motor of the present invention thereby provides direct conversion of periodic motion to rotary motion, maintaining the small distance, high force nature of the motor to produce low speed, high torque output.
The invention shall now be described in detail with reference to the following drawings in which:
In a first embodiment of the invention, a motor is disclosed, comprising a stator of high permeability material having a magnetic core, magnetic windings, and an internal cavity which is preferably cylindrical; and a rotor made from ferromagnetic materials with high permeability, situated inside the stator. Preferably, said rotor is internal to said stator and said rotor has an outer diameter significantly smaller than the inner diameter of the stator. The outer diameter of the rotor and the inner diameter of the stator have gear teeth so that the rotor and stator mesh as eccentric gears.
Preferably, said windings comprise a set of electrical coils positioned in slots, channels, or cavities in the high permeability material. The coils are arranged to induce a magnetic field in the high permeability material of the rotor and stator and any gap between, thereby creating magnetic attractive force between the rotor and the stator.
During operation, the stator windings are selectively and sequentially energized such that a magnetic normal force is induced around the circumference of the stator, such that the force revolves around the internal cavity of the stator, attracting the rotor to different portions of the stator, whereby the rotor is caused to roll without slipping upon the inner surface of the stator cavity.
The contact patch between the rotor and the stator thus moves in rapid circular periodic motion around the inner circumference of the stator. The rotor rolls on the inside of the stator, thus it oscillates with high frequency and has a slow overall speed and rotational rate.
The interaction between rotor and stator can be explained as follows: In the region of the energized coils, the motion of the rotor is essentially radial, with the rotor moving toward the stator over a short distance with minimal lateral motion. High ‘normal force’ attraction thus causes the motion of the rotor. The size difference between rotor and stator converts this radial motion into rotational motion as the rotor rolls without slipping upon the inner surface of the stator cavity. High torque, low speed rotary motion may be achieved thereby without a requirement for high-speed low torque rotary motion. The rotor will be seen to oscillate at relatively high frequency, but with small displacement and therefore small acceleration, this high frequency small displacement motion being converted to high torque, slow speed rotary motion.
Preferably, said motor comprises constraining means for constraining said driven member to a path of movement with respect to said fixed member. Said constraining means are preferably bearings for constraining the driven member to a fixed path while absorbing oscillation and transmitting rotation. An example of such bearings are those labeled 4 in
Alternatively said rotor is external to said stator, said stator is externally toothed, said rotor is internally toothed, and the external diameter of said stator is slightly smaller than the internal diameter of said rotor such that when magnetic normal force is induced around the circumference of the stator, such that the force circles the internal cavity of the stator, said rotor is periodically attracted around the outside of said stator, such that the contact patch between the rotor and the stator moves in rapid circular periodic motion around the outer circumference of the stator, thus oscillating with high frequency and slow overall speed and rotational rate.
An advantage of the present invention is that high torques can be obtained due to the use of radial magnetic force, unlike regular motors which primarily use the much smaller tangential magnetic forces. A further advantage of the invention is that the slow relative speed between components causes minimal wear and tear of the gears and minimal frictional losses. A yet further advantage of the invention is that, due to the gear teeth, high torques can be accommodated without the risk of slip.
A further advantage is that, since the combination of eccentric bearings and gear teeth supporting the rotor constrain said rotor to roll without slipping, there is no dependence on friction for output torque production, which eliminates magnetic effort used to hold the rotor to the stator against gear separation forces, and maintains rotor-stator distance to an optimal value for magnetic and mechanical design.
In order to clarify the operation of a motor driven by ‘magnetic normal force’, the simplest possible implementation of such a motor is now presented. This is for the purpose of clarification and, while it could be a possible embodiment, it is not the preferred one: A plate pivots at the center of a ratchet wheel. The pivot plate has a pawl which meshes with the ratchet wheel, such that when the electromagnet pulls on the pivot plate, the plate and ratchet wheel move, but when the electromagnet turns off the pivot plate returns to its start position and the ratchet pawl clicks along the ratchet wheel. Thus the pivot plate tips back and forth under power from the electromagnet, and the ratchet wheel slowly spins.
The preferred embodiment of the invention is uses ‘hypocyclic’ gearing. In hypocyclic gearing, two gear elements interact. One gear element is permitted to rotate, the other is held in a fixed orientation (that is, a fixed angle relative to a reference line). One gear element has a fixed position, and the other oscillates or ‘wobbles’ in a circular path. Either element can take either of the two characteristics; that is, either one element oscillates and one rotates; or one is fixed and the other both oscillates and rotates.
With this ‘conventional’ hypocyclic approach, neither gear element rotates at very high speed, however the contact point between the two gear elements moves at the oscillation frequency. This means that the gear teeth mesh at high speed, and the rubbing between gear teeth is similar to that seen with the gears rotating at very high speed. Thus although all parts move at low speed, there is a very high torque and the wear and friction is similar to that seen at high speed.
An object of the present invention is to reduce the friction and wear, by reducing the gear meshing friction. By way of illustration, consider the example ratchet system described above: when the magnet is energized and pulls on the pivot plate, the pawl is stationary on the tooth of the ratchet wheel, thus there is no significant wear. When the magnet is de-energized, the pawl rubs on the back of the tooth, but the force is low thus wear is greatly reduced. That is, wear is reduced when force is applied at a time when the parts are stationary relative to each other. In a conventional hypocyclic system the gears are moving at different rates thus are not stationary relative to each other.
Generally, in embodiments of the present invention, the oscillating element is electromagnetically driven with two distinct motions: conventional hypocyclic circular oscillating motion; and rotation about the center of a concentric element. The oscillating element is arranged on a bearing to be able to rotate about the concentric element.
During operation, there are thus two stages: one is concentric motion, that is, rotation about the same center for both the oscillating and concentric gear elements. Here there is no relative motion, thus wear is reduced. The second is, when oscillation is released and concentric motion locked, the system operates in a standard hypocyclic fashion but under no force, thus there is movement without force, thus less wear. The locking and releasing is achieved using magnetic actuation suitably phased with the main drive force.
Thus the system operates using concentric motion driven by normal magnetic force, combined with hypocyclic motion.
The first, preferred, embodiment of the invention is shown in
The eccentric bearing assembly forces the wobbler gear to follow the proper circular path and acts to resist the gear separation force.
The bearing arrangement (or constraining means comprising transmission means) of
An alternative bearing arrangement is shown in
In a further alternative bearing arrangement, bearings are manufactured with three races and two eccentric rings of balls.
In a further alternative bearing arrangement shown in
Means other than bearings may be used to permit high frequency oscillation and transmit slow rotation.
In one alternative, an Oldham Coupler or variation on such a coupler, or similar coupling arrangement may be used to permit oscillation and transmit rotation.
In a further alternative shown in
In a further alternative shown in
In a further alternative shown in
In a further alternative, rheostatic fluids may be used as constraining and transmission means.
In further alternatives, springs, flexures, or tension elements, combined with a single centered offset bearing, are used. It will be readily understood that many configurations are possible to permit oscillation and transmit rotation, and this patent is not limited to those described herein.
Stator 1 may have any number of poles, and may be formed from any magnetic metal or other magnetic material. A characteristic of stator 1 is that is has internal gear teeth as well as magnetic windings. Various configurations are possible for the gear teeth of stator 1.
Preferably, said gear teeth of said stator are positioned an axial distance away from at least one edge of said stator, at a radius larger than the largest radius of the end turns of the windings, as shown in
Alternatively, the stator gear teeth may be formed into the face of the internal cavity of the stator (the geared surface thus being integral to the magnetic surface), and the rotor gear teeth positioned accordingly.
Alternatively, as shown in
Alternatively, the stator may comprise several such layers of magnetic stator alternated with several such layers of internally toothed stator. The rotor may comprise several such layers of magnetic rotor alternated with several such layers of externally toothed rotor.
As a further alternative, said internal cavity of said stator may be of trapezoidal cross-section. Said rotor would therefore be of triangular cross section. An advantage of this is that, whereas with a cylindrical cross section, less than half of the winding interacts with the airgap, in this case almost ⅔ of the winding interacts with the airgap.
Alternatively, in place of gear teeth, magnetorheological fluids may be used. Such fluids become stiff in the presence of a magnetic field. The fluid may be located between said rotor and said stator and may be contained in a region between said rotor and said stator such that when the rotor is pulled towards contact with the stator, the fluid is present in the space between rotor and stator (i.e. the point which would be the point of contact if there were not fluid preventing contact). Since the magnetic field is strongest at the point of contact, the fluid thus becomes stiff at this point. The point of stiffness moves with the movement of the rotor. The magnetorheostatic fluid is thus able to provide means of preventing slip between rotor and stator at high torque, and means of absorbing oscillation and transmitting rotation.
Furthermore, a separate magnetic field may be used to control the magnetorheostatic fluid. This separate field may be out of phase with the main, torque-producing field. The torque-producing field may lead the fluid-controlling field slightly, thus allowing the fluid to be stiff at the point of contact of rotor and stator, while the main attracting force between rotor and stator is slightly ahead of this point to provide continuous motion. Any other phase configuration or other configuration of separate magnetic fields may be used corresponding to the shape and requirements of the particular rotor and stator.
Several arrangements are possible for the magnetic windings. The windings may be arranged radially or tangentially.
Preferably, the magnetic windings are wound down one slot, across one end of the stator to the next consecutive slot, up the next slot and back across the other end of the stator. Thus each winding surrounds one saliency between two consecutive slots, without one winding overlapping another. In other words, each winding has a span value of one. This reduces the amount of winding taken up as end turns, which do not provide flux. The saliencies may be of any size although saliencies covering a larger angle are preferred as this is a more flux-efficient arrangement.
The magnetic windings may also span more than one saliency between slots and may overlap each other. The magnetic windings may also be wound toroidally, i.e. up through a slot of the stator and radially outwards at one end of the stator, down along the external circumference of the stator and radially inwards at the other end of the stator. This configuration requires shorter end turns and therefore fewer windings. Any other workable winding configuration may be used which will cause magnetic flux to pass in a closed loop between the stator and the rotor in such a way as to attract the rotor to the stator in a radial direction.
The magnetic windings may be wound around horseshoe stator saliencies as shown in
Furthermore buried horseshoe windings may be used, that is, horseshoe windings having saliencies along the circumference. This is equivalent to a toroidal winding where the stator is distorted to make more room for the coils, and is shown in
As a further alternative, the transverse flux windings may be combined with permanent magnets, either on the rotor or the stator. In this arrangement, the permanent magnets tend to pull the rotor against the side of the system, providing the lateral holding necessary to hold the gears together. The electromagnets strengthen the magnetic field on one side of the contact patch between rotor and stator, and weaken it on the other side of said contact patch, providing rotational force to rotate the rotor.
Furthermore, in place of conventional motor windings, radial solenoids may be used. As shown in
A specific example of the numbers of teeth of the stator and eccentric geared rotor will now be given, without limitation. In the eccentric system, the contact patch between the rotor and stator moves at high speed. The rotor is essentially be wobbling back at forth at the same frequency, but no part of the system is actually rotating at high speed. An internally toothed stator may be 13″ in diameter with 320 teeth, and an externally toothed rotor may be 12.5″ in diameter with 308 teeth. Although this cannot be described in terms of regular gear ratios, since the contact patch rotates 27 times for each rotation of the rotor, this can be termed a 27:1 ‘eccentric gear ratio’. Here, instead of rotating 27 times, the rotor has wobbled back and forth by M″ 27 times each time it rotates once.
The following is an analysis of the available attractive force and in terms of the gear teeth of the above specific example.
The gears may be 3″ thick, of which 2.25″ can be counted as being part of the magnetic circuit. Attractive force can only be applied when the two gears are within 0.1″ apart. Approximately ¼ of the entire circumference of the stator is available for attraction. However, to achieve motion, a trailing portion of the stator must be demagnetized while a leading portion is magnetized. Therefore, only approximately ⅛ of the circumference is available for active application of the magnetic field. Thus there is a region of approximately 2.25″×5″ in which magnetic force can be applied, at a pressure of 150 PSI. This produces 1700 pounds of attractive force, using normal materials, without overstressing the magnetic materials. Using suitable high saturation density materials such as hiperco alloys, flux densities in excess of 2.2 T may be achieved, resulting in attractive pressure in excess of 250 PSI.
In a second embodiment of the invention, shown in
During operation, the stator is magnetized in such a way that the rotor is pulled around the internal cavity of the stator, eccentrically oscillating at high frequency and rotating. Since the rotor is coupled to the spline, the spline rotates with the rotor but flexes to accommodate the eccentric oscillation of the rotor, thus only the rotation is transmitted by the spline to the output shaft. An advantage of this arrangement is that the motor can be integrally combined with the gearing.
Preferably, the internal surface of the stator is toothed. Preferably, the flexible spline is externally toothed and is made from flexible, non-magnetic material, for example but without limitation, spring temper steel. Alternatively, the spline gear teeth may be made from individual pieces of rigid metal such as hardened steel which are attached, for example by welding, to the flexible spline but do not themselves form a solid ring. The spline has a few less gear teeth than the stator.
Alternatively, the motor is arranged as shown in
Alternatively there is no wave generator and the spline is made from magnetic material. The internal surface of the stator and the external surface of the spline are toothed and engage each other. The spline has a few less teeth than the stator. During operation, pairs of opposite sections of the stator 1 are magnetised together, in a periodic cycle. For example, in a twelve-pole stator, the windings at 0 and 180 degrees are magnetised, then the windings at 30 and 210 degrees, then the windings at 60 and 240 degrees, then the windings at 90 and 270 degrees, etc. The spline is distorted by this magnetic field into contact with the stator at two points, 180 degrees apart. The rotation of the field causes the spline to rotate with the field. The external teeth of the spline engage the internal teeth of the stator, thus the spline oscillates at high frequency with the rotation of the field, and rotates slowly due to the small difference in number of teeth. The spline is coupled to the output shaft, thus only the slow rotation of the spline is transmitted to the output shaft. An advantage of this arrangement over the wave generator arrangement is that there are no parts rotating at high speed. A disadvantage is that some magnetic force is used up in distorting the spline and is therefore not available for output torque generation. However, because the spline is a spring, magnetic energy used to distort the spline may be recovered as electrical energy regenerated as the spline relaxes.
Stator 1 may have any number of windings, and may be formed from any magnetic metal or other magnetic material. In the case where stator 1 has internal gear teeth as well as magnetic windings, various configurations are possible for the gear teeth of stator 1.
Preferably, said gear teeth of said stator are positioned axially distanced from at least one edge of said stator, at a radius larger than the largest radius of the end turns of the windings, as shown in
Alternatively, the stator gear teeth may be formed into the face of the internal cavity of the stator and the spline rotor gear teeth positioned correspondingly.
In the case of an eccentric rotor coupled to a spline, the rotor may be coupled to the spline by being mounted inside the spline, such that magnetic forces pull the rotor around, the rotor pushes the spline teeth against the stator teeth and the spline engages the stator and rotates against it. In this arrangement, magnetic material is incorporated into the spline. Alternatively, the rotor may be toothed and engage the internally toothed stator directly, and protrude from the internal cavity of the stator. The protruding portion of the rotor may then be coupled to the internal teeth of the spline.
Several arrangements are possible for the magnetic windings. The windings may be arranged radially or tangentially.
Preferably, the magnetic windings are wound down one slot, across one end of the stator to the next consecutive slot, up the next slot and back across the other end of the stator. Thus each winding surrounds one saliency between two consecutive slots, without one winding overlapping another. In other words, each winding has a span value of one. This reduces the amount of winding taken up as end turns, which do not provide flux. The saliencies may be of any size although saliencies covering a larger angle are preferred as this is a more flux-efficient arrangement.
The magnetic windings may also span more than one saliency between slots and may overlap each other. The magnetic windings may also be wound toroidally, i.e. up through a slot of the stator and radially outwards at one end of the stator, down along the external circumference of the stator and radially inwards at the other end of the stator. This configuration requires shorter end turns and therefore fewer windings. Any other workable winding configuration may be used which will cause magnetic flux to pass in a closed loop between the stator and the rotor in such a way as to attract the rotor to the stator in a radial direction.
The magnetic windings may be wound around horseshoe stator saliencies as shown in
Furthermore, in place of conventional motor windings, radial solenoids may be used. As shown in
In a third embodiment of the invention, a motor is disclosed, comprising a stator having a magnetic core, magnetic windings, and a cylindrical internal cavity; and at least two planetary gear rotors made from magnetically conductive materials, situated inside the stator. The third embodiment is shown in
Stator 1 may have any number of poles, and may be formed from any magnetic metal or other magnetic material. A characteristic of stator 1 is that is has internal gear teeth as well as magnetic windings. Various configurations are possible for the gear teeth and magnetic windings of stator 1.
Preferably, said gear teeth of said stator are positioned on at least one edge of said stator, at a radius larger than the largest radius of the end turns of the windings, as shown in
Alternatively, the stator gear teeth may be formed into the face of the internal cavity of the stator and the sun and planet gear teeth sized accordingly.
Alternatively, the stator may comprise a layer of magnetic stator 26 and a layer of internally toothed stator 23, mechanically joined by any suitable joining means such as tongue and groove, adhesive, etc. Such a stator is shown in
Alternatively, the stator may comprise several such layers of magnetic stator alternated with several such layers of internally toothed stator. The rotors may comprise several such layers of magnetic rotor alternated with several such layers of externally toothed rotor. The sun gear may comprise several layers of toothed gear on an output shaft, alternated with empty space, or one long toothed gear, or any workable configuration.
Several arrangements are possible for the magnetic windings. The windings may be arranged radially or tangentially.
Preferably, the magnetic windings are wound down one slot, across one end of the stator to the next consecutive slot, up the next slot and back across the other end of the stator. Thus each winding surrounds one saliency between two consecutive slots, without one winding overlapping another. In other words, each winding has a span value of one. This reduces the amount of winding taken up as end turns, which do not provide flux. The saliencies may be of any size although saliencies covering a larger angle are preferred as this is a more flux-efficient arrangement.
The magnetic windings may also span more than one saliency between slots and may overlap each other. The magnetic windings may also be wound toroidally, i.e. up through a slot of the stator and radially outwards at one end of the stator, down along the external circumference of the stator and radially inwards at the other end of the stator. This configuration requires shorter end turns and therefore fewer windings. Any other workable winding configuration may be used which will cause magnetic flux to pass in a closed loop between the stator and the rotor in such a way as to attract the rotor to the stator in a radial direction.
The magnetic windings may be wound around horseshoe stator saliencies as shown in
Furthermore, in place of conventional motor windings, radial solenoids may be used. As shown in
In a fourth embodiment of the invention, shown in
Magnetic normal force is induced around the circumference of the stator, at different angular positions of the stator periodically, such that the eccentric ring gear rotor is periodically attracted to different regions around the stator, such that the contact patch between the ring gear rotor and the stator moves in circular periodic motion around the inner circumference of the stator. The ring gear rotor engages the smaller concentric gear, oscillating around it such that the contact patch between the ring gear rotor and the smaller concentric gear moves in circular periodic motion around the smaller concentric gear. The rotor oscillates with high frequency and slowly rotates. Only the slow rotation is transmitted to the smaller concentric gear, which drives the output shaft. An advantage of this design is that it ensures minimal gear tooth wear since at any one time the load is spread over many gear teeth compared with, for example, an planetary gear arrangement. A further advantage is that arrangement can be made for decoupling the stator from the concentric gear by moving the ring gear rotor concentric with the output shaft, for example for high speed operation.
Stator 1 may have any number of poles, and may be formed from any magnetic metal or other magnetic material. A characteristic of stator 1 is that is has internal gear teeth as well as magnetic windings. Various configurations are possible for the gear-teeth and magnetic windings of stator 1.
Preferably, said gear teeth of said stator are positioned on at least one edge of said stator, at a radius larger than the largest radius of the end turns of the windings. Stator 1 has slots 24 in which the windings are positioned. End turns 22 occupy space at the end of the stator. Only one end turn is shown, for diagrammatic clarity. Gear teeth 23 of the stator are positioned at the edge of the stator, at a greater radius than that of end turns 22, as shown. This is shown in
Alternatively, the stator gear teeth may be formed into the face of the internal cavity of the stator. In this case, the ring gear rotor gear teeth need not extend radially outwards from the magnetic body of the ring gear rotor.
Alternatively, the stator may comprise a layer of magnetic stator 26 and a layer of internally toothed stator 23, mechanically joined by any suitable joining means such as tongue and groove, adhesive, etc. This is shown in
Alternatively, the stator may comprise several such layers of magnetic stator alternated with several such layers of internally toothed stator. The ring gear rotor may comprise several such layers of magnetic rotor alternated with several such layers of externally toothed rotor. The concentric gear may be one cylindrical gear as long as the ring gear rotor, with teeth extending along its whole length, or with teeth extending along only the length corresponding to the ring gear rotor teeth, or the concentric gear may extend only to the length corresponding to the ring gear rotor teeth, or any other workable arrangement.
Several arrangements are possible for the magnetic windings. The windings may be arranged radially or tangentially.
Preferably, the magnetic windings are wound down one slot, across one end of the stator to the next consecutive slot, up the next slot and back across the other end of the stator. Thus each winding surrounds one saliency between two consecutive slots, without one winding overlapping another. In other words, each winding has a span value of one. This reduces the amount of winding taken up as end turns, which do not provide flux. The saliencies may be of any size although saliencies covering a larger angle are preferred as this is a more flux-efficient arrangement.
The magnetic windings may also span more than one saliency between slots and may overlap each other. The magnetic windings may also be wound toroidally, i.e. up through a slot of the stator and radially outwards at one end of the stator, down along the external circumference of the stator and radially inwards at the other end of the stator. This configuration requires shorter end turns and therefore fewer windings. Any other workable winding configuration may be used which will cause magnetic flux to pass in a closed loop between the stator and the rotor in such a way as to attract the rotor to the stator in a radial direction.
The magnetic windings may be wound around horseshoe stator saliencies as shown in
Furthermore, in place of conventional motor windings, radial solenoids may be used. As shown in
In a fifth embodiment of the invention, shown in
Note that in
Stator 1 may have any number of poles, and may be formed from any magnetic metal or other magnetic material.
Various configurations are possible for the gear teeth of the fifth embodiment.
A preferred arrangement for the gear teeth of the fifth embodiment is shown in
Alternatively, there may be more than one layer of the magnetic (rotor-stator) plane and/or more than one layer of the gear plane. This would add rigidity and ruggedness to the motor. The layers may be mechanically joined by any suitable joining means such as tongue and groove, adhesive, etc.
Several arrangements are possible for the magnetic windings in the stator. The windings may be arranged radially or tangentially.
Preferably, the magnetic windings are wound down one slot, across one end of the stator to the next consecutive slot, up the next slot and back across the other end of the stator.
Thus each winding surrounds one saliency between two consecutive slots, without one winding overlapping another. In other words, each winding has a span value of one. This reduces the amount of winding taken up as end turns, which do not provide flux. The saliencies may be of any size although saliencies covering a larger angle are preferred as this is a more flux-efficient arrangement.
The magnetic windings may also span more than one saliency between slots and may overlap each other. The magnetic windings may also be wound toroidally, i.e. up through a slot of the stator and radially outwards at one end of the stator, down along the external circumference of the stator and radially inwards at the other end of the stator. This configuration requires shorter end turns and therefore fewer windings. Any other workable winding configuration may be used which will cause magnetic flux to pass in a closed loop between the stator and the rotor in such a way as to attract the rotor to the stator in a radial direction.
The magnetic windings may be wound around horseshoe stator saliencies as shown in
Furthermore, in place of conventional motor windings, radial solenoids may be used. As shown in
In a sixth embodiment of the invention, shown in
The rotors 42 have oversized holes at their centers and may have bearings, to accommodate their eccentric oscillation about the output shaft 6.
An advantage of this embodiment compared with the first embodiment is that forces are balanced over the whole motor. A further advantage is that the geared layer magnetically insulates the two magnetic layers from each other, preventing either magnetic layer from interfering with the flux pattern of the other.
Preferably, there are two magnetic layers and one gear layer. Each rotor and corresponding stator is one magnetic layer, and the two rotor gears and the output gear form the geared layer. The geared layer magnetically insulates the two magnetic layers from each other.
Alternatively, there may be more than two magnetic layers and/or more than one geared layer. This would add rigidity and ruggedness to the motor. It is preferable to have an even number of magnetic layers, to balance the forces in the motor. It is also preferable for the number of geared layers to be equal to one less than the number of magnetic layers, with magnetic layers on each outside end. It is further preferable for the layers to be arranged alternately, i.e. magnetic layer, geared layer, magnetic layer, geared layer, magnetic layer etc. An example is shown in
For all arrangements, the layers may be mechanically joined by any suitable joining means such as tongue and groove, adhesive, etc.
Several arrangements are possible for the magnetic windings in the stators. The windings may be arranged radially or tangentially.
Preferably, the magnetic windings are wound down one slot, across one end of the stator to the next consecutive slot, up the next slot and back across the other end of the stator. Thus each winding surrounds one saliency between two consecutive slots, without one winding overlapping another. In other words, each winding has a span value of one. This reduces the amount of winding taken up as end turns, which do not provide flux. The saliencies may be of any size although saliencies covering a larger angle are preferred as this is a more flux-efficient arrangement.
The magnetic windings may also span more than one saliency between slots and may overlap each other. The magnetic windings may also be wound toroidally, i.e. up through a slot of the stator and radially outwards at one end of the stator, down along the external circumference of the stator and radially inwards at the other end of the stator. This configuration requires shorter end turns and therefore fewer windings. Any other workable winding configuration may be used which will cause magnetic flux to pass in a closed loop between the stator and the rotor in such a way as to attract the rotor to the stator in a radial direction.
The magnetic windings may be wound around horseshoe stator saliencies as shown in
Furthermore, in place of conventional motor windings, radial solenoids may be used. As shown in
In a seventh embodiment of the invention, a ratchet and pawl mechanism is used, as shown in
The above specificities of the seven embodiments described in detail are not limiting to the scope of the invention and it will be readily seen that many further variations and ramifications of this invention—the direct use of the much larger magnetic normal force instead of tangential force to drive a motor—are possible.
For example, the fixed member described herein may be an externally toothed stator and the driven member described herein may be an externally toothed rotor placed outside the stator. As another example, the fixed member may have an internal cavity having polygonal cross-section the driven member may have a polygonal cross-section having fewer sides than that of the fixed member. As another example, the fixed member may be a screw thread and the driven member a screw. As a further example, the fixed member may be a rack and the driven member may be a pinion.
Pairs of motors may be used together, oscillating as mirror images of each other, in order to balance out the asymmetric forces caused by the eccentric oscillation.
For a fixed member with a cylindrical, internally-toothed cavity and a cylindrical, externally-toothed driven member, a clutch mechanism may be provided in which a spring tends to pull the driven member concentric with the fixed member. When the magnetic field is applied, the driven member is pulled against the fixed member, and the motor operates. When no field is applied, the spring pulls the driven member concentric with the fixed member and no motor operation or wear takes place.
Furthermore, using balanced forces and magnetic bearing techniques, this clutch mechanism could be used to operate the motor as an induction motor at high speed, to provide low torque, and as the motor of the present invention at low speed, to provide high torque. The spring would be used to pull the driven member out of mechanical contact with the fixed member at low speeds, and balanced forces and known bearing techniques applied to cause the driven member to spin within the fixed member without mechanical contact, as in a regular induction motor. At low speeds, magnetic fields would be applied to overcome the force from the spring, bringing the driven member into mechanical contact with the fixed member and causing the motor to operate as in the first embodiment of the present invention.
Furthermore, eccentric bearings may be used as a clutch. Thus the eccentric bearing approach of
As a further possibility, a cam ring may be used as shown in
As a further alternative, the invention may comprise a fixed member comprising at least one magnetic winding, having an internal cavity and a driven member comprising magnetically conductive materials, said driven member being able to move within, said fixed member, wherein magnetic normal force is induced in said fixed member periodically, whereby said driven member is periodically moved by magnetic force with respect to said fixed member, whereby any sort of periodic motion is produced. The motion may be oscillatory, reciprocal, or motion of any other shape or form.
In all of the above wherein magnetic normal force has been used to drive a high frequency oscillation which is converted into low speed, high torque rotation, the rotor both oscillated and rotated. As a final alternative for this invention, the rotor may be centrally mounted on the output shaft and may rotate slowly, without oscillating, and the stator may oscillate about the rotor. This simplifies the bearings arrangements, since the rotor is on standard bearings which permit it to rotate, and these same bearings may support the output, e.g. the driven wheel. The stator may be mounted on eccentric bearings and may oscillate eccentrically. The eccentric stator bearings may be mounted on a stationary plate, and their position may be adjustable. In particular, the eccentric stator bearings may be adjustable in and out radially, enabling the stator to be selectively centered in the rotor (disconnecting the bearings) or driven against the rotor (connecting the bearings). Adjusting the bearings in this manner may be used to provide a clutch for the motor.
It will be readily appreciated that many further arrangements of apparatus will also comprise embodiments of this invention, and the scope of the invention should be determined by the appended claims.
This application is a Continuation-in-Part of U.S. application Ser. No. 11/900,475 filed on Sep. 11, 2007, which claims the benefit of U.S. Provisional Patent Application No. 60/843,933, filed Sep. 11, 2006, and is a Continuation-in-part of International Patent Application No. PCT/US2007/05523, filed Mar. 2, 2007, which designates the United States. Said International Patent Application No. PCT/US2007/05523 claims the benefit of U.S. Provisional Patent Application No. 60/778,667, filed Mar. 3, 2006. This application also claims the benefit of U.S. Provisional Application No. 60/993,412 filed on Sep. 11, 2007. The aforementioned documents are herein incorporated in their entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60843933 | Sep 2006 | US | |
| 60778667 | Mar 2006 | US | |
| 60993412 | Sep 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11900475 | Sep 2007 | US |
| Child | 12283379 | US | |
| Parent | PCT/US2007/005523 | Mar 2007 | US |
| Child | 11900475 | US |
