Abstract
An axial flux machine includes a rotor having: a first and a second rotor disk; a shifting element; a first and a second pair of mechanical mating elements, enabling an axial displacement of the first respectively second rotor disk relative to the shifting element by rotating the first respectively second rotor disk. An equal rotation of the first and the second rotor disk results in an equally-sized but opposite axial displacement of the first and second rotor disk; a coupling element, mechanically coupling the first and the second rotor disk, thereby blocking a rotation of the first rotor disk relative to the second rotor disk while allowing for an axial displacement.
Claims
1.-14. (canceled)
15. An axial flux machine comprising: a shaft having a rotational axis in axial direction; a stator having a central axis corresponding to the rotational axis, and comprising a plurality of coils, and a rotor comprising a first and a second rotor disk having a central axis corresponding to the rotational axis, wherein the first and the second rotor disk are mounted on both sides of the stator, each of the rotor disks being axially separated from the stator by an air gap and comprising permanent magnets, wherein the rotor comprises: a shifting element, rotatably mounted while secured in axial direction relative to the stator; a first and a second pair of mechanical mating elements, adapted to mate the shifting element and the first respectively second rotor disk, and enabling an axial displacement of the first respectively second rotor disk relative to the shifting element by rotating the first respectively second rotor disk relative to the shifting element, wherein an equal rotation of the first and the second rotor disk relative to the shifting element, results in an equally sized but opposite axial displacement of the first and second rotor disk relative to the shifting element; a coupling element, mechanically coupling the first and the second rotor disk, thereby blocking a rotation of the first rotor disk relative to the second rotor disk while allowing for an axial displacement of the first rotor disk relative to the second rotor disk, and wherein: the first respectively second pair of mechanical mating elements comprises a first respectively second guiding spline, adapted to mesh with a corresponding spline comprised in the first respectively second rotor disk, the first guiding spline and the second guiding spline both being comprised in a cylindrical surface of the shifting element; the coupling element comprises a third guiding spline, adapted to mesh with a corresponding spline comprised in the first respectively second rotor disk, the third guiding spline being comprised in a cylindrical surface of the coupling element; the shifting element and the coupling element are separate elements mounted coaxially, the cylindrical surface of the coupling and shifting element having a central axis corresponding to the rotational axis.
16. The axial flux machine according to claim 15, wherein the axial flux machine comprises an actuator, the actuator comprising one or more axially displaceable parts, and adapted to push the first and the second rotor disk apart by an axial movement of the one or more axially displaceable parts.
17. The axial flux machine according to claim 16, wherein the actuator comprises a first and a second axially displaceable wall, both positioned between the first and the second rotor disk, wherein the first respectively second wall is in contact with the first respectively second rotor disk.
18. The axial flux machine according to claim 17, wherein the actuator comprises a fluid chamber adapted to receive a hydraulic fluid, and wherein the fluid chamber comprises the first and the second axially displaceable wall, such that an axial displacement of the first and second rotor disk changes the volume of the fluid chamber.
19. The axial flux machine according to claim 18, wherein the volume of the fluid chamber is controlled based on a hydraulic pressure.
20. The axial flux machine according to claim 15, wherein the shifting element is separate from the coupling element, thereby allowing for a rotation of the shifting element relative to the coupling element during an axial displacement of the first and second rotor disk.
21. The axial flux machine according to claim 15, wherein the cylindrical surface comprising the first and second guiding spline faces the cylindrical surface comprising the third guiding spline.
22. The axial flux machine according to claim 15, wherein the shifting element is integrated in the shaft.
23. The axial flux machine according to claim 15, wherein the path of the first guiding spline describes a left-handed helix, and the path of the second guiding spline describes a right-handed helix.
24. The axial flux machine according to claim 15, wherein the third guiding spline is adapted to establish one or more tongue-and-groove connections between the coupling element and the first respectively second rotor disk.
25. The axial flux machine according to claim 15, wherein the third guiding spline comprises one or more straight ribs extending in axial direction, said one or more ribs being adapted to mesh with one or more straight grooves comprised in the first and second rotor disk and extending in axial direction.
26. The axial flux machine according to claim 15, wherein the rotor further comprises one or more springs positioned between the first and the second rotor disk, the one or more springs adapted to push the first and the second rotor disk apart.
27. A method for realizing mechanical field weakening in an axial flux machine, comprising: providing an axial flux machine having a rotational axis in axial direction, the axial flux machine comprising a stator and a rotor, the stator having a central axis corresponding to the rotational axis and comprising a plurality of coils, and the rotor comprising: a first and a second rotor disk having a central axis corresponding to the rotational axis, wherein the first and the second rotor disk are mounted on both sides of the stator, each of the rotor disks being axially separated from the stator by an air gap and comprising permanent magnets, a shifting element, rotatably mounted while secured in axial direction relative to the stator; a first and a second pair of mechanical mating elements, mating the shifting element and the first respectively second rotor disk, the first respectively second pair of mechanical mating elements comprising a first respectively second guiding spline, adapted to mesh with a corresponding spline comprised in the first respectively second rotor disk, the first guiding spline and the second guiding spline both being comprised in a cylindrical surface of the shifting element; a coupling element, mechanically coupling the first and the second rotor disk, and comprising a third guiding spline, adapted to mesh with a corresponding spline comprised in the first respectively second rotor disk, the third guiding spline being comprised in a cylindrical surface of the coupling element; wherein the shifting element and the coupling element are separate elements mounted coaxially, the cylindrical surface of the coupling and shifting element having a central axis corresponding to the rotational axis; axially moving the first rotor disk relative to the shifting element by the first pair of mechanical mating elements, due to rotating the first rotor disk relative to the shifting element, and axially moving the second rotor disk relative to the shifting element by the second pair of mechanical mating elements, due to rotating the second rotor disk relative to the shifting element, wherein an equal rotation of the first and the second rotor disk relative to the shifting element, results in an equally-sized but opposite axial displacement of the first and second rotor disk relative to the shifting element; blocking a rotation of the first rotor disk relative to the second rotor disk by the coupling element during the axial displacement of the first and second rotor disk.
28. The method according to claim 27, further comprising: providing an actuator comprising one or more axially displaceable parts; axially moving the one or more axially displaceable parts, thereby pushing the first and second rotor disk apart.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] FIG. 1 shows a three-dimensional representation of an axial flux machine according to an embodiment of the invention. For clearness of representation, a part of the machine has been intersected in the drawing.
[0056] FIG. 2 and FIG. 3 show a three-dimensional representation of a shifting element, a coupling element and one of the rotor disks, according to an embodiment of the invention. In FIG. 3, the coupling element has been intersected in the drawing.
[0057] FIG. 4 shows a three-dimensional representation of a first and a second rotor disk according to an embodiment of the invention.
[0058] FIG. 5 shows a three-dimensional representation of a shifting element according to an embodiment of the invention.
[0059] FIG. 6 shows a three-dimensional representation of a rotor disk mounted on a shifting element, according to an embodiment of the invention.
[0060] FIG. 7 shows a three-dimensional representation of a coupling element according to an embodiment of the invention. For clearness of representation, the coupling element has been intersected in the drawing, showing only half of the element.
[0061] FIG. 8 shows a three-dimensional representation of a coupling element mounted on two rotor disks, according to an embodiment of the invention. For clearness of representation, the components have been partly intersected in the drawing.
[0062] FIG. 9 shows a cross-section according to a plane comprising the rotational axis, of a stator and a coupling element mounted on two rotor disks, according to an embodiment of the invention.
[0063] FIG. 10 and FIG. 11 show a cross-section according to a plane comprising the rotational axis, of a motor shaft and a coupling element mounted on two rotor disks, according to an embodiment of the invention, and illustrates the use of a hydraulic actuator for initiating the displacement of the rotor disks.
[0064] FIG. 12 shows a motor shaft and a cross-section according to a plane comprising the rotational axis of a coupling element mounted on two rotor disks, according to an embodiment of the invention, and illustrates the use of a spring, in addition to a hydraulic actuator.
[0065] FIG. 13 shows a three-dimensional representation of a rotor disk mounted on a shifting element, according to another embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENT(S)
[0066] FIG. 1 shows an axial flux machine 100 according to an embodiment of the invention, comprising a motor shaft 104, a stator 103, a first rotor disk 101 and a second rotor disk 102. The machine 100 has a rotational axis 110, defining the axial direction. The stator 103 comprises coils 107, typically copper windings wound around a ferromagnetic core, and the rotor disks 101, 102 comprise permanent magnets 108. The rotor disks 101, 102 are mounted on the shaft 104, on both sides of the stator 103, leaving a small air gap between a rotor disk 101, 102 and the stator 103. Bearings 109 are provided to mount the shaft 104 rotatably in a static housing.
[0067] The axial flux machine 100 comprises a shifting element 105 and a coupling element 106. These two elements, together with the rotor disk 102, are shown in FIG. 2 and FIG. 3. As will further be explained underneath, the particular cooperation between the shifting element 105 and the coupling element 106 provides for a unique synchronisation mechanism, ensuring a synchronous displacement of the two rotor disks 101 and 102.
[0068] FIG. 4 shows the first rotor disk 101 and the second rotor disk 102, being separated from the other machine components. As is indicated on the figure for the second rotor disk 102, a rotor disk comprises a ring-shaped portion 405 and cylindrical portion 406. The cylindrical portion 406 protrudes from the surface of the ring-shaped portion 405. The ring-shaped portion 405 carries the permanent magnets 108. In order to contribute to the synchronisation mechanism, the rotor disks 101, 102 comprise two particular features. First, each rotor disk 101, 102 comprises a spline 401, 402, also referable as a mating element 401, 402, provided on the inner surface of the cylindrical portion 406. The splines 401, 402 are adapted to mesh with the shifting element 105, as will be described in detail below. In the shown embodiment, the spline 401, 402 is a helical spline, comprising grooves defining a helical path along the cylindrical inner surface. Secondly, each rotor disk 101, 102 comprises a spline 403, 404, provided on the outer surface of the cylindrical portion 406. The splines 403, 404 are adapted to mesh with the coupling element 106, as will be described in detail below. In the shown embodiment, the splines 403, 404 are provided as straight grooves 403, 404 extending in axial direction.
[0069] FIG. 5 individually shows the shifting element 105. In the shown embodiment, the shifting element 105 is integrated in the rotor shaft 104, meaning that it is part of the rotor shaft 104, as is also clear from FIG. 1. The shifting element 105 comprises a first guiding spline 501 and a second guiding spline 502, embodied as grooves in the cylindrical outer surface of the shifting element 105. The path of the first guiding spline 501 describes a left-handed helix, and the path of the second guiding spline 502 describes a right-handed helix, both having the same pitch. The first guiding spline 501 of the shifting element 105 is adapted to mesh with the corresponding spline 401 of the first rotor disk 101. In other words, the first guiding spline 501 of the shifting element 105 and the spline 401 of the first rotor disk 101, together form a first pair of mechanical mating elements, thereby mating the first rotor disk 101 and the shifting element. Analogously, the second guiding spline 502 of the shifting element 105 and the spline 402 of the second rotor disk 102, together form a second pair of mechanical mating elements, thereby mating the second rotor disk 101 and the shifting element 105. This is further illustrated in FIG. 6, where the second rotor disk 102 is shown, mounted on the shifting element 105.
[0070] The pairs of mechanical mating elements 501-401 and 502-402 define the trajectory that a rotor disk 101, 102 may follow when moving relatively to the shifting element 105. Indeed, when changing the angular position of a rotor disk 101, 102 relatively to the shifting element 105, the rotor disk 101, 102 moves axially with respect to the shifting element 105. Moreover, the pairs of mating elements 501-401 and 502-402 are chosen such that an equal rotation of the first 101 and the second rotor disk 102 relative to the shifting element 105 results in an equally sized but opposite axial displacement of the rotor disks 101, 102.
[0071] FIG. 7 individually shows the coupling element 106. In the shown embodiment, the coupling element 106 has a cylindrical shape, comprising a cylindrical sleeve 703 as an outer surface, and comprising a third guiding spline 700 provided on the inner surface. The third guiding spline 700 comprises straight ribs 701 extending in axial direction, alternating with straight grooves 702. The third guiding spline 700 is adapted to mesh with the corresponding splines 403 and 404 comprised in the first rotor disk 101 respectively the second rotor disk 102. This is illustrated in FIG. 8, showing that the straight ribs 701 of the coupling element 106 may slide in the straight grooves 403, 404 of the rotor disks, thereby establishing a tongue-and-groove type of connection between the coupling element 106 and the first respectively second rotor disk 101, 102. On the one hand, the coupling element 106 mechanically connects or couples the two rotor disks 101, 102. On the other hand, the coupling element 106, together with the corresponding splines 403, 404 on the rotor disks, defines a specific trajectory when moving the rotor disks 101, 102 relatively to coupling element 106. Indeed, the coupling is such that an axial displacement of the first rotor disk 101 relative to the second rotor disk 102 is possible while a rotation of the first rotor disk 101 relative to the second rotor disk 102 is blocked. This is illustrated in FIG. 8, wherein (a) shows a condition with the two rotor disks 101, 102 close to each other, and (b) a condition after displacing the rotor disks 101, 102 away from each other.
[0072] In FIG. 3, the assembly formed by the shifting element 105, the coupling element 106 and the rotor disks 101, 102 is illustrated. For clearness of representation, only one rotor disk 102 is shown. In the shown embodiment, the coupling element 106 and the shifting element 105 are mounted coaxially, having a central axis corresponding to the rotational axis 110, with the shifting element 105 positioned internally with respect to the coupling element 106. The shown elements together provide a unique synchronisation mechanism, wherein the shifting element 105 allows to axially move the rotor disks 101, 102 while rotating relatively to the shifting element 105, and the coupling element 106 guaranties that the angular position of both rotor disks 101, 102 always remains the same. In this way, the rotor disks 101, 102 will move synchronously, in axial direction over the same distance but in opposite sense.
[0073] FIG. 9 further illustrates the effect of the provided synchronisation mechanism. FIG. 9 (a) shows a condition in which the rotor disks 101, 102 are positioned closely to the stator 103, leaving a small air gap 901, 902 on both sides of the stator 103. Typically, this corresponds to a high-torque low-speed operation of the axial flux motor. FIG. 9 (b) shows another condition in which the rotor disks 101, 102 are positioned further away from the stator 103, leaving a larger air gap 903, 904 on both sides of the stator 103. In this mode, the permanent magnetic field in the stator 103 is weakened, thus allowing for a low-torque high-speed operation of the axial flux motor. Due to the synchronous movement of both rotor disks 101, 102 during repositioning, the air gaps 901 and 902, respectively 903 and 904, always have the same length. Consequently, the use of the described synchronisation mechanism enables mechanical field weakening to be applied in an axial flux motor with a one statortwo rotors topology.
[0074] FIG. 10 and FIG. 11 illustrates the use of a hydraulic actuator 1000 in an axial flux machine according to the embodiment described in the previous figures. The actuator 1000 comprises a fluid chamber 1002 and a fluid supply 1001. The fluid supply 1001 is implemented as a bore in the motor shaft 104, through which a hydraulic fluid under pressure is supplied to the fluid chamber 1002. The bore 1001 runs through one half of the shaft length, and may connect to a hydraulic coupling at one end of the motor shaft 104. The fluid chamber 1002 comprises a first wall 1101 and a second wall 1102, which are positioned between the rotor disks 101, 102 and are connected to the first respectively second rotor disk 101, 102. The walls 1101 and 1102 are axially displaceable, meaning that their position relative to the motor shaft 104 may be changed according to the axial direction. Due to an increase of the hydraulic pressure, an axial force 1103, 1104 is exerted on the first respectively second wall 1101, 1102, thereby axially displacing the walls 1101, 1102, and increasing the volume of the fluid chamber 1002. Accordingly, the rotor disks 101, 102 are pushed apart, thereby initiating an axial movement of the rotor disks 101, 102. Due to the shifting element 105, this axial movement is accompanied by a change of the angular position of the rotor disks 101, 102 relative to the shifting element 105. Moreover, thanks to the synchronisation mechanism described above, both rotor disks 101, 102 will move away from each other in a synchronous way: even when initially the increased hydraulic pressure is absorbed by only one of the rotor disks, the synchronisation mechanism ensures that any initial movement of one rotor disk will automatically result in a synchronous movement of the other rotor disk. When decreasing the hydraulic pressure, such that the magnetic attraction force between a rotor disk 101, 102 and the stator prevails, the rotor disks 101, 102 will return to a position closer to the stator 103, again in a synchronous way. As is clear from the figure, only one hydraulic actuator 1000, using a single source of energy is present, thereby allowing for a simple integration in the machine.
[0075] FIG. 12 illustrates the use of a spring 1200, in addition to the hydraulic actuator 1000. In the shown embodiment, a helical spring 1200 is positioned between the cylindrical portions 407, 406 of the rotor disks 101, 102. The spring 1200 is in compressed condition, such that it pushes the first and second rotor disk 101, 102 apart. When used in combination with a hydraulic actuator 1000, the spring 1200 and hydraulic actuator 1100 together provide the axially force pushing the rotor disks 101, 102 apart. In another embodiment, not shown in the drawings, a spring like in FIG. 12 may be positioned between the rotor disks 101, 102, but without any actuator being present. In such a case, actuation may just rely on the change of torque from the rotor disks 101, 102 when evolving towards a high-speed low-torque operation or vice versa.
[0076] Finally, FIG. 13 shows another embodiment of the synchronisation mechanism. Compared to the first embodiment described in FIGS. 1 to 9, the position of the shifting element and the coupling element is switched. Indeed, in the second embodiment, shown in FIG. 13, the coupling element 1300 is integrated in the motor shaft 104. The coupling element 1300 comprises a guiding spline, embodied as straight grooves 1301, 1302 extending in axial direction. The straight grooves 1302 are adapted to mesh with corresponding straight ribs 1305, the latter being provided on the inner surface of the cylindrical portion 1306 of the second rotor disk 1304. Similarly, the straight grooves 1301 are adapted to mesh with straight ribs comprised in the first rotor disk, the latter not being shown in FIG. 13. Moreover, the rotor disk 1304 comprises a spline 1303, provided as teeth describing a helical path on the outer surface of the cylindrical portion 1306 of the second rotor disk 1304. The spline 1303 is adapted to mesh with a corresponding guiding spline provided on the shifting element. The shifting element is not shown on FIG. 13, but it is clear from the figure that the shifting element may have a cylindrical shape, with grooves describing a helical path provided on the inner surface, and may be mounted coaxially with the coupling element 1300. In this way, an assembly similar to the assembly of FIG. 3 is obtained, wherein the shifting element of the second embodiment has a position similar to the coupling element 106 of the first embodiment, and the coupling element 1300 of the second embodiment has a position similar to the shifting element 105 of the first embodiment.
[0077] Although the present invention has been illustrated by reference to specific embodiments, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied with various changes and modifications without departing from the scope thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. In other words, it is contemplated to cover any and all modifications, variations or equivalents that fall within the scope of the basic underlying principles and whose essential attributes are claimed in this patent application. It will furthermore be understood by the reader of this patent application that the words comprising or comprise do not exclude other elements or steps, that the words a or an do not exclude a plurality, and that a single element, such as a computer system, a processor, or another integrated unit may fulfil the functions of several means recited in the claims. Any reference signs in the claims shall not be construed as limiting the respective claims concerned. The terms first, second, third, a, b, c, and the like, when used in the description or in the claims are introduced to distinguish between similar elements or steps and are not necessarily describing a sequential or chronological order. Similarly, the terms top, bottom, over, under, and the like are introduced for descriptive purposes and not necessarily to denote relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and embodiments of the invention are capable of operating according to the present invention in other sequences, or in orientations different from the one(s) described or illustrated above.
