A MAGNETIC GEAR ARRANGEMENT

The present invention relates to magnetic gear arrangements . Gearboxes and gear arrangements are generally utilised in a wide range of situations in order to couple drive mechanisms. Traditionally, gear wheels have been utilised in order to create gearboxes and gearbox arrangements, but it will be understood that such gearboxes tend to require use of lubricating oils which can make them unattractive for areas which may become contaminated by such lubricating oils, where the lubricating oil is a fire hazard or in hot or cold environments where the oil viscosity varies or in a low pressure environment where the oil may evaporate. Furthermore, gearboxes using gear wheels may be particularly noisy making them unacceptable for low noise environments such as in hospitals, libraries and residential areas.

More recently magnetic gearboxes have been provided which comprise respective gear rotors with pole members between them. The rotors incorporate permanent magnets and the pole member, or pole pieces or elements, act to modulate the magnetic flux transferred between the gear rotors in order to create a gearbox operation. The attached Fig. marked "prior art" shows a typical magnetic gearbox arrangement 1 in which an outer gear rotor or wheel 2 is arranged to rotate coaxially with an inner gear rotor or wheel 3 with pole members 4 between them. Generally, if one gear rotor is turned this causes the other gear to rotate in the reverse direction. The pole members are typically made from laminated ferromagnetic material and act to modulate the magnetic field produced by each gear rotor 2 , 3 so that the polarity of the modulation product matches the polarity of the magnetic field of the other gear rotor 2, 3. Alternatively, the pole members 4 may be mounted upon their own rotor typically referred to as a middle gear. In such circumstances, if the inner gear rotor 3 is fixed, the pole member rotor or middle gear will rotate in response to the rotation of the outer gear rotor

2. If the outer gear rotor 2 is fixed, the middle rotor or rotor incorporating the pole members 4 will rotate in response to rotation of the inner gear rotor 3. In such circumstances the magnetic gearbox arrangement behaves in a fashion typical of an epicyclical gearbox arrangement as depicted to the side of the magnetic gearbox arrangement 1 in the prior art figure. This epicyclical gearbox 10 comprises an annulus 12, sun 13 and planet gears 14. Thus, it will be appreciated that in the magnetic gearbox arrangement 1 the outer gear rotor 2 acts as the annulus or ring, the pole members 4 and its rotor act as the planet gears 14 and the inner gear rotor acts as the sun 13 in the epicyclical gearbox comparison.

It will be understood that, as previously, if the pole members 4 are ^■ kept stationary the gear ratio equals the ratio of the magnetic poles on < the inner gear rotor to the magnetic poles on the outer gear rotor. The number of pole members 4 equals the sum of the pole pairs on both gear rotors 2, 3. For further information it will be appreciated that the inner and outer rotor gears may be replaced by an electrical machine winding to form a gear winding so that the magnetic gearbox arrangement 1 may act as a generator if mechanical power is supplied to drive rotation of the gear windings or act as a motor if electric power is supplied to the windings.

Although effective as a gearbox arrangement such as an epicyclical gearbox, a magnetic gearbox arrangement 1 configured to act in an epicyclical manner requires that the input and output shafts to the rotors 2, 3 are coaxial. Such positioning of the input and output shafts may not be convenient .

In accordance with aspects of the present invention there is provided a magnetic gear arrangement comprising a first gear rotor and a second gear rotor and a pole member associated between the first gear rotor and the second gear rotor, the first gear rotor and the second gear rotor displaced relative to each other and the pole member extended therebetween to allow a lateral and/or radial

displaced relationship between the first gear rotor and the second gear rotor relative to an axis of rotation for the gear arrangement .

Typically, the first gear rotor and/or the second gear rotor ^■ have permanent magnets. Additionally, or alternatively, the first gear rotor and the second gear rotor have electrical windings to create electro magnetic effects.

Typically, the first gear rotor and the second gear rotor are substantially aligned relative to each other. Alternatively, the first gear rotor and the second gear rotor are substantially non-aligned.

Advantageously, the pole member surrounds the first gear rotor and/or the second gear rotor. Alternatively or additionally, the pole member extends into the first gear rotor and/or the second gear rotor.

Possibly, the pole member is particularly shaped in order to provide displacement between the first gear rotor and the second gear rotor. Potentially, the pole member comprises a plurality of pole elements secured in a housing. Possibly, the housing is a rotor.

Potentially, the pole member incorporates electrical windings. Typically, the electrical windings incorporate a respective switch. Possibly, the switch is arranged to provide an open circuit configuration and a closed circuit configuration for its respective electric winding. Additionally, the switch is configured to provide a variable impedance load through the respective electrical winding. Aspects of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: -

Fig. 1 is a schematic illustration of a magnetic gear arrangement in accordance with aspects of the present invention;

Fig. 2 is a schematic front view of a first gear rotor as utilised in Fig. 1;

Fig. 3 is a schematic front view of a second gear rotor as utilised in accordance with Fig. 1;

Fig. 4 is a schematic side cross section of an offset magnetic gear arrangement in accordance with aspects of the present invention;

Fig. 5 is a schematic side view of a right angled bevelled magnetic gear arrangement in accordance with aspects of the present invention;

Fig. 6 is a schematic cross section of a second magnetic gearbox arrangement in accordance with aspects of the present invention; Fig. 7 is a schematic front view of a first gear rotor in accordance with the arrangement depicted in Fig. 6;

Fig. 8 is a schematic front view of a second gear rotor utilised in accordance with the arrangement depicted in Fig. 6; Fig. 9 is a schematic side cross section of an offset gear arrangement in accordance with further aspects of the present invention;

Fig. 10 is a schematic cross section of a bevelled gear arrangement in accordance with aspects of the present invention;

Fig. 11 is a schematic cross section of a gear arrangement incorporating inner and outer gear rotors in accordance with aspects of the present invention;

Fig. 12 is a schematic front view of an outer gear rotor as utilised in accordance with the arrangement depicted in Fig. 11;

Fig. 13 is a schematic front view of an inner gear rotor as . utilised in accordance with the arrangement depicted in Fig. 11; Fig. 14 is a schematic cross section of a concentric and coaxial gear arrangement in accordance with aspects of the present invention;

Fig. 15 is a schematic front view of a gear rotor as utilised in the arrangement depicted in Fig. 14; Fig. 16 is a schematic front view of a second gear ratio utilised in accordance with the arrangement depicted in Fig. 14;

Fig. 17 is a schematic side cross section of a variable gear rotor gear arrangement in accordance with aspects of the present invention;

Fig. 18 is a schematic front view of a first gear rotor as utilised in the arrangement depicted in Fig. 17;

Fig. 19 is a schematic front view of a second gear rotor as utilised in accordance with the arrangement depicted in Fig. 17, and:

Fig. 20 is a schematic side cross section of a variable gear rotor arrangement in accordance with aspects of the present invention with hinges.

As indicated above, magnetic gear arrangements can be configured in order to achieve an epicyclical gearbox mode of operation. However, difficulties arise with prior magnetic gear arrangements in that the gear rotors or wheels must overlap and rotate concentrically about the axis of rotation for the arrangement with the pole members in between. Such an arrangement may be inconvenient.

Figs. 1 to 3 illustrate schematically a first gear arrangement 21 in which gear rotors 22, 23 are arranged to be located inside a pole member 24. The gear rotors 22, 23 comprise respectively a rotor hub 25, 26 upon which permanent magnets 27, 28 are located to allow interaction with the pole member 24. The pole member 24 itself incorporates magnetic poles as distinct elements or pieces such that through magnetic field modulation magnetic circuits are created whereby rotation of one of the gear rotors 22, 23 causes rotation of the other gear rotor 22,

23. The rotors 22, 23 are secured to respective shafts 29, 30 to provide the mechanical drive couplings as required.

It will be appreciated it is the rotation of the gear rotors 22, 23, and in particular the magnets 27, 28, past the poles in the member 24 which stimulates modulation through the poles in the member 24 and therefore follower movement of the coupled other gear rotor 22, 23.

As indicated previously, the pole member 24 is typically formed from laminated ferromagnetic materials in order to provide the poles through which the magnetic fields are modulated between the rotors 22, 23.

In the embodiment of the invention depicted in Figs. 1 to 3 it will be understood that the rotors 22, 23 rather than being concentric are arranged in a displaced relationship along a coaxial axis of rotation A-A. This displaced relationship is achieved through extending the pole member 24 to create a situation where the gear rotors 22, 23 are inside the pole member 24. Such displacement may be useful in providing couplings between drive machinery but furthermore allows, through appropriate shaping of a pole member 44 as depicted in Fig. 4, offset of a first gear rotor 42 and a second gear rotor 43. Thus, the axis of rotation B-B, C-C for the respective gear rotors 42, 43 are offset relative to each other. As indicated, this offset is achieved by utilisation of a pole member 44 which includes a stagger section 45 to accommodate the offset. The pole member 44, as indicated, will generally be formed from a laminated ferromagnetic material and is arranged to incorporate pole elements which allow modulation of the magnetic field interactions of the respective rotors 42, 43 due to rotation of the shafts 39, 40.

As indicated above, the pole member in accordance with aspects of the present invention acts as a conduit through which magnetic field modulation is transferred between the gear rotors of the gear arrangement . Generally, the pole member will comprise an integral housing incorporating the pole elements presented in alignment with the rotor. However, a pole member in the form of a cage comprising a number of pole elements secured together could be provided if required, nevertheless it will generally be more convenient to secure these pole elements in a housing.

As indicated, the pole member may be shaped to achieve the necessary magnetic field modulation. It is also possible to create a bevel gear transfer arrangement as depicted in Fig. 5. Thus, as previously, the arrangement 51 has a first gear rotor 52 and a second gear rotor 53 associated with pole members 54 in order that the rotors 52, 53 can be in a substantially perpendicular relationship. However, it will also be understood that the

rotors 52, 53 could be presented to each other at other angles as desirable and subject to appropriate shaping of the pole member 54. The rotors 52, 53 are respectively- secured to shafts 49, 50. In the embodiment depicted in Fig. 5 the shaft 49 may be a main power shaft for machines with the gear rotor 52 utilised in order to drive ancillary machinery through the gear rotor 53 and its shaft 50. As previously, magnetic interaction as the rotors 52, 53 engage with the pole member 54 will cause reciprocal rotation in a gear ratio dependent upon the relative pole numbers in the rotors 52, 53 as well as pole members 54.

In order to accommodate the shaft 49 it will be appreciated that the pole member 54 may be shaped to avoid fouling of the shaft 49 if it extends far beyond the rotor 52. Nevertheless it will be appreciated that the pole members 54 act as pole elements which are typically perpendicular to the rotors 52, 53 for appropriate interaction.

It will be appreciated in some situations it may be more desirable to provide a gear arrangement which although continuing to act and rotate coaxially arranges the gear rotors to act externally at the outside of the pole member. Figs. 6 to 8 illustrate an embodiment in accordance with aspects of the present invention in which a first gear rotor 62 and a second gear rotor 63 are arranged with a pole member 64 in a situation where the pole member 64 comprises a number of pole elements arranged in a cylindrical relationship within the rotors 62, 63. The rotors 62, 63 are associated with respective shafts 59, 60 through cages 71, 72. Thus, the gear rotors are connected to the shafts 59, 60 through the cage arrangements 71, 72 in order to transfer drive etc.

Each rotor 62, 63 comprises a ferromagnetic cage incorporating magnetic poles which will interact with the pole member 64 in order to create magnetic circuits for modulation and therefore transfer of rotation across the pole member between the rotors 62, 63 and therefore shafts 59, 60.

As previously, the inside pole member configuration of a gear arrangement in accordance . with aspects of the present invention can also be adapted to provide an offset gear arrangement and a bevel gear arrangement . These further embodiments of aspects of the present invention are respectively depicted in Figs. 9 and 10.

In Fig. 9 a first gear arrangement 91 comprises a first gear rotor 92 and a second gear rotor 93 associated together through a pole member 94. As previously, the pole member 94 may comprise a number of individual pole elements formed into a cage or integral housing, but in any event shaped such that the axis of rotation D-D, E-E of shafts 89, 90 are offset relative to each other. In such circumstances as previously, it is by appropriate shaping of the pole member 94, and in particular the pole elements, that this offset is achieved. These pole elements and pole member 94 act to provide modulation of the magnetic fields across rotation as driven by either shaft 89, 90.

Fig. 10 illustrates a bevel gear configuration for an outer gear rotor with inner pole member configuration. Thus, the arrangement 101 has a first gear rotor 102 and a second gear rotor 103 arranged in a perpendicular relationship although other angles of presentation could be provided through appropriate shaping of a pole member 104. The pole member 104 as previously comprises a number of pole elements to allow magnetic field modulation between the rotors 102, 103. As previously, shafts 99, 100 associated through cages with the rotors 102, 103 provide rotational drive for one rotor 102, 103 and then through the magnetic field modulation reciprocal rotation in an appropriate gear ratio in the other rotor 102, 103 and therefore its shaft 99,100.

It will be appreciated in accordance with aspects of the present invention it is by appropriate shaping of the pole member 104 that displacement whether it be longitudinally or along a co-axis of rotation, radially either side of that axis of rotation or in terms of angular presentation can be achieved between respective gear rotors. It will also be understood that the pole member

can be shaped and assembled from pole elements to match differing gear rotor types and sizes. Thus, as illustrated in Figs. 11 to 13 , a magnetic gear arrangement can be provided where the pole member is arranged to be inside a first gear rotor 112, and outside a second gear rotor 113. In such circumstances the pole member 114 again modulates magnetic fields due to rotation of the gear rotors 112, 113 in order to provide power transfer across the arrangement

111 between a shaft 109 associated through a cage 120 with the first gear rotor 112 whilst the second gear rotor 113 has a shaft 110. In such circumstances, greater variability with regard to the gear ratios between the rotors 112, 113 can be achieved. It will also be understood that by appropriate shaping of the pole member offset and bevel arrangements can also be provided as described previously.

Figs: 12 and 13 respectively show the first gear rotor

112 and the second gear rotor 113. As can be seen, the first gear rotor , 112 has a cylindrical cross section with the pole member 114 presented on the inner surface of the first gear rotor 112 whilst, as shown in Fig. 13, the second gear rotor 113 is arranged with the pole elements of the pole member 114 external to the rotor 113. In such circumstances as described previously, the pole elements in the pole member 114 will modulate magnetic fields between the respective rotors 112, 113 in order to provide magnetic coupling in the gear ratio dependent upon the number of magnetic poles in the respective rotors 112, 113.

As indicated above, with magnetic gear arrangements a number of rotational configurations are possible. With regard to aspects of the present invention typically the pole member is stationary so that the gear rotors can rotate. This will be the most practical configuration particularly in situations where there is offset and bevel arrangements between the gears as described above. Nevertheless it will be understood where coaxial rotation is possible, then the pole member may be mounted on a gear ring rotor itself so that then both the gear rotors as well as the pole member can rotate as a whole . In such

circumstances, one of the rotors could be kept stationary with the other gear rotor and pole member rotating as described above in order to create epicyclical gear operation. It will also be understood that a conventional magnetic gear arrangement comprising concentric gear rotors with a pole member between them could be combined into an arrangement in accordance with aspects of the present invention. Thus, as depicted in Figs. 14 to 16 a first conventional concentric gear arrangement comprises a first rotor 152 and a second gear rotor 153 whilst a second conventional concentric gear arrangement 143 comprises a first gear rotor 162 and a second gear rotor 163. As indicated above, these conventional concentric gear arrangements 142, 143 will operate with a pole member comprising a number of pole elements or pieces between the respective rotors 152', 153; 162, 163 in order to provide a gear ratio for magnetic coupling between the respective rotors 152, 153; 162, 163 to shaft 159, 160. These pole elements 154, 164 as described previously will modulate the magnetic fields between the respective rotors 152, 153; 162, 163.

In accordance with aspects of the present invention each concentric gear arrangement 142, 143 will itself be associated through _ a pole member assembly 144 extending between the arrangements 142, 143 in order to couple in magnetic modulation the respective rotation of the rotors 152, 162 across the arrangement 141.

It will be understood that the respective gears 152, 153; 162, 163 are slightly displaced in Fig. 14 in order to show their position but in reality the rotors will generally be overlapping and wholly concentric to maximise magnetic interaction.

It, will again be understood through appropriate shaping of the pole member 144 offset gear and bevel gear arrangements can be provided.

As indicated previously, the pole elements in the pole member provide rotating magnetic circuits with the rotors of a gear arrangement in accordance with aspects of the

present invention. In such circumstances by altering the impedance of these pole elements it will be understood that adjustments can be made to the circulating magnetic fields and therefore alteration in the gear ratio achieved. Figs. 17 to 19 illustrate schematically a potential means for adjusting gear ratio in a gear arrangement 171 in accordance with aspects of the present invention.

In Figs. 17 and 19 a first gear rotor 172 is associated with a second gear rotor 173 through pole members 174 arranged about the rotors 172, 173. The rotors 172, 173 are associated with shafts 179, 180 in order to transfer drive across the arrangement 171. Each of the pole members 174 incorporates an electrical winding 175 which can vary the impedance of the pole member 174. Each winding 175 may incorporate a simple switch to enable the winding to be configured as either closed circuit or open circuit with differing effect upon the impedance of the pole member 174. It will also be understood that the windings may be arranged to allow variable impedance to range from open circuit to close circuit providing a greater degree of adjustability of the impedance within the pole member 174 and therefore the gear ratio of the arrangement 171.

By simple switching between open circuit and closed circuiting of the windings 175 on some or all of the pole members 174 it will be understood that there is a reduction in the rate of change of magnetic flux in the respective pole member 174 potentially removing them from service and therefore the gear ratio of the arrangement 171. By connecting variable resistances to the windings 175 through appropriate switching it will be understood that the varying resistances between infinite (open circuit) and zero again varies the magnetic coupling and modulation effect of the respective pole member 174 between the gear rotors 172, 173 in order to achieve a potential clutch function between the rotors 172, 173 and therefore the shafts 179, 180.

As indicated previously, magnetic gear arrangements can be provided which generate electricity. In such

circumstances, in the arrangement 171 it will be appreciated that the magnetic fields in the pole members 174 generate voltages in the windings 175 which can then be tapped off as generated electricity. Alternatively, in order to supply or supplement mechanism power in the arrangement 171 if electrical energy is provided to the windings 175 then mechanical power in terms of enhanced magnetic field modulation across the arrangement will be added to improve torque and mechanical power transfer between the shafts 179, 180.

In the above circumstances, it will be appreciated that through the windings 175 the gear arrangement 171 may act as an electrical machine with appropriate control mechanisms . By aspects of the present invention it will be appreciated that shaping of the pole members, in particular the pole elements forming that pole member, allows displacement of the respective gear rotors so that these rotors are not forced to be concentric enabling gear arrangements which are offset or bevelled or otherwise more convenient in operational use.

As it is the pole members which transfer the magnetic field between the gear rotors in accordance with aspects of the present invention, it will be appreciated that if these pole members are made flexible then adjustability in use may be achieved. Typically, as indicated, the pole members will be formed from a ferromagnetic material in order to achieve enhanced magnetic modulation performance. Such materials will allow formation of pole members which are flexible or incorporate hinges or flexible joints. Fig. 20 illustrates such a flexible embodiment of a gear arrangement in accordance with aspects of the present invention. Thus, the arrangement 201 has a first gear rotor 202 and a second gear rotor 203 associated through a pole member 204 comprising a number of pole elements which extend between the rotors 202, 203. In accordance with the embodiment depicted in Fig. 20 hinges 205 are provided to allow flexibility in the member 204. Such flexibility will allow relative movement or realignment of the axes X-X, Y-Y

of the respective shaft 199, 200. This could have particular advantages where the respective rotors 202, 203 are not mounted upon a common rigid chassis or where there may be vibrational or transient movements of the respective shafts 199, 200 in operation.

As indicated above, hinges 205 are one possibility with regard to providing flexibility in an arrangement in accordance with aspects of the present invention. Alternatively, the pole member 204, as indicated could be made from pole elements in the form of ferromagnetic wires, insulated from each other to prevent eddy current losses but extending between the rotors 202, 203. Furthermore, flexibility could be created through forming flexible tubes containing magnetic particles, e.g., ferrite dust. The flexible tubes could also be filled with a ferro fluid, that is to say a colloidal suspension of magnetic particles or even liquid oxygen which has magnetic properties in order to transfer magnetic field through appropriate modulation between the rotors 202, 203. It will be appreciated that gear arrangements in accordance with aspects of the present invention can be utilised in a wide range of situations where a gear box is required.

It is to be noted that in all the embodiments that there is an arrangement of a plurality of discrete, separate, pole elements in the magnetic gear arrangements. These pole elements are arranged circumferentially, or have a cylindrical geometry. The pole elements do not form a continuous circumferential magnetic circuit and improve the magnetic coupling between the first gear rotor and the second gear rotor. The discrete pole elements allow the manufacture and assembly of offset and bevel gear arrangements . The use of individual windings around the discrete pole elements allow the magnetic flux in each pole element to be controlled independently of other pole elements .

The pole elements are arranged circumferentially with respect to the axis of rotation of the first gear rotor and

they are arranged circumferentially with respect to the axis of rotation of the second gear rotor.