Abstract
A method for manufacturing an axial flux machine adapted for generating a magnetic flux along the axis of rotation, includes the manufacturing of one or more stators, having the following steps: providing a surface comprising one or more flat support surfaces perpendicular to the axis of rotation; positioning one or more boundary elements, individual stator elements, and a ring element on the one or more support surfaces. At least one of the boundary elements is a cooling element adapted for conducting heat. The stator elements each has a ferromagnetic core and an electric winding wound around the ferromagnetic core, and filling the empty space between the outer circumference, the stator elements and the ring element with an electrically insulating filling material.
Claims
1.-15. (canceled)
16. A method for manufacturing an axial flux machine adapted for generating a magnetic flux along the axis of rotation, said method comprising the manufacturing of one or more stators, wherein the manufacturing of said stator comprises the following steps: providing a surface comprising one or more flat support surfaces perpendicular to said axis of rotation; positioning one or more boundary elements, individual stator elements, and a ring element on said one or more support surfaces, wherein at least one of said boundary elements is a cooling element adapted for conducting heat; wherein said stator elements each comprise a ferromagnetic core and an electric winding wound around said ferromagnetic core, and wherein after positioning, said one or more boundary elements together form an outer circumference, said individual stator elements and said ring element being situated within said outer circumference, and said individual stator elements being positioned around said ring element, and filling the empty space between said outer circumference, said stator elements and said ring element with an electrically insulating filling material.
17. The method for manufacturing an axial flux machine according to claim 16, wherein positioning said one or more boundary elements and said individual stator elements takes place on the basis of one or more position jigs, wherein the one or more position jigs are part of said stator after manufacturing.
18. The method for manufacturing an axial flux machine according to claim 16, wherein said support surfaces on which said individual stator elements are being positioned, are in one plane, and wherein the dimension measured along said axis of rotation is the same for each of said individual stator elements.
19. The method for manufacturing an axial flux machine according to claim 18, wherein said support surfaces on which said ring element and said one or more boundary elements are being positioned, are in the same plane as the said support surfaces on which said individual stator elements are being positioned, and wherein the dimension measured along said axis of rotation is the same for said ring element, said one or more boundary elements and said stator elements.
20. The method for manufacturing an axial flux machine according to claim 16, wherein said one or more boundary elements are multiple individual boundary elements.
21. The method for manufacturing an axial flux machine according to claim 20, wherein said individual boundary elements are all individual cooling elements that are adapted for conducting heat.
22. The method for manufacturing an axial flux machine according to claim 16, wherein said ring element is the outer ring of a radial bearing, wherein one of said support surfaces is a disk adapted for receiving the inner ring of said radial bearing, wherein the dimension measured along said axis of rotation is larger for said inner ring than it is for said outer ring, and wherein the manufacturing of said stator further comprises the following step: positioning said radial bearing with said inner ring on said disk and with said outer ring around said inner ring.
23. The method for manufacturing an axial flux machine according to claim 16, wherein said cooling element comprises one or more elongated components which are positioned between two of said individual stator elements, and wherein said cooling element comprises one or more elongated components which during positioning are externally oriented relative to said outer circumference.
24. The method for manufacturing an axial flux machine according to claim 23, wherein said elongated components comprise slits, arranged along a direction perpendicular to said axis of rotation.
25. The method for manufacturing an axial flux machine according to claim 16, wherein said method further comprises the manufacturing of one or more rotors, and wherein manufacturing said rotor comprises the following steps: providing a surface comprising one or more flat support surfaces perpendicular to said axis of rotation; positioning two annular elements and magnets on said one or more support surfaces, wherein after positioning, said magnets are situated between said annular elements; filling the empty space between said magnets and said annular elements with an electrically insulating filling material.
26. The method for manufacturing an axial flux machine according to claim 25, wherein manufacturing said rotor further comprises: positioning ferromagnetic material on said one or more support surfaces, wherein after positioning, said ferromagnetic material is situated between said annular elements.
27. The method for manufacturing an axial flux machine according to claim 26, wherein said ferromagnetic material is a helical ribbon.
28. The method for manufacturing an axial flux machine according to claim 21, comprising mounting a rotor on said inner ring of said radial bearing.
29. An axial flux machine manufactured according to the method of claim 16.
30. A wind turbine comprising an axial flux machine according to claim 27, wherein said axial flux machine is adapted for generating electric power, wherein said wind turbine further comprises: blades adapted for converting wind power into rotational energy; a shaft that is fixedly mounted to the base of said wind turbine, and wherein said blades are mounted with bearings to said shaft; a cable system comprising cables which at an outer end are attached to points on said blades and which at another outer end are attached to fixing points, wherein said stator is fixedly mounted to said shaft, and wherein said rotor is fixedly connected to said fixing points.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 is a 3D-reproduction of a stator according to an embodiment of the invention.
[0054] FIG. 2 is a cross-section of a stator perpendicular to the axis of rotation according to an embodiment of the invention.
[0055] FIG. 3 is a cross-section of a stator perpendicular to the axis of rotation according to another embodiment of the invention.
[0056] FIG. 4 is a 3D-reproduction of a stator element according to an embodiment of the invention.
[0057] FIG. 5 is a cooling element according to an embodiment of the invention, shown in a 3D-reproduction and in a cross-section perpendicular to the axis of rotation.
[0058] FIG. 6 is a cooling element according to another embodiment of the invention, shown in a 3D-reproduction and in a cross-section perpendicular to the axis of rotation.
[0059] FIG. 7 is a cooling element according to another embodiment of the invention, shown in a 3D-reproduction.
[0060] FIG. 8a and FIG. 8b show a cross-section of the stator along the axis of rotation, according to an embodiment of the invention.
[0061] FIG. 9a is a block diagram of the method for manufacturing a stator according to an embodiment of the invention.
[0062] FIG. 9b is a cross-section along the axis of rotation of a flat table used in the manufacturing of a stator according to an embodiment of the invention.
[0063] FIG. 10 is a 3D-reproduction of a rotor according to an embodiment of the invention.
[0064] FIG. 11 is a cross-section of a rotor perpendicular to the axis of rotation according to an embodiment of the invention.
[0065] FIG. 12a and FIG. 12b show a cross-section of the rotor along the axis of rotation according to an embodiment of the invention.
[0066] FIG. 13a is a block diagram of the method for manufacturing a rotor according to an embodiment of the invention.
[0067] FIG. 13b is a cross-section along the axis of rotation of a flat table used in the manufacturing of a rotor according to an embodiment of the invention.
[0068] FIG. 14 is a 3D-reproduction of two rotors mounted on a stator according to an embodiment of the invention.
[0069] FIG. 15 is a cross-section along the axis of rotation of two rotors mounted on a stator according to an embodiment of the invention.
[0070] FIG. 16 is a 3D-reproduction of a wind turbine, along the front side, according to an embodiment of the invention.
[0071] FIG. 17 is front view of a wind turbine according to an embodiment of the invention.
[0072] FIG. 18 is a 3D-reproduction of a wind turbine, along the rear side, according to an embodiment of the invention.
[0073] FIG. 19 is a cross-section along the axis of rotation of a wind turbine according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0074] FIG. 1 shows a 3D-reproduction of a stator (100) after manufacturing according to an embodiment of the invention. FIG. 2 shows a cross-section perpendicular to the axis of rotation of this stator (100). In the embodiment shown, the stator (100) is a disk of a specific thickness, measured along the axis of rotation, in the center of which there is an aperture intended for the shaft of the machine.
[0075] FIG. 1 and FIG. 2 show a stator ring (100) wherein the inner circumference is formed by a ring element (103) and the outer circumference is formed by boundary elements (102). The stator ring (100) forms an integral unit, bounded by the ring element (103) and the boundary elements (102), the stator elements being anchored in a filling material (105). In the embodiment of FIG. 1 and FIG. 2, the ring element (103) is the outer ring of a radial bearing. The ring element (103) could also be referred to as a race element (103) or outer race (103). The radial bearing may be of any suitable type known in the state of the art, such as a ball bearing, roller bearing, slide bearing, . . . . In the embodiment of FIG. 2, the radial bearing is a ball bearing having an outer ring (103) or outer race (103), inner ring (104) or inner race (104) and balls (202). Typically, the radial bearing is tailored to this application, but if necessary the use of an available bearing of standard dimensions is also possible. Typically, the inner ring (104) of the bearing is mounted on a shaft, which during operation of the generator permits the stator (100) to be kept in a stationary position while the shaft rotates. The embodiment of FIG. 1 and FIG. 2 is advantageous as no extra part is required to form the inner circumference of the stator ring, as this function is performed by the outer ring (103) of the bearing. This limits the number of parts. However, the invention is not limited to this embodiment. In an alternative embodiment, the ring element (103) is a separate part forming the inner boundary of the stator (100), and a separate bearing is mounted on top of it. For instance, the ring element (103) is a tailor-made metal ring having a specific thickness measured along the axis of rotation. Typically, the ring element (103) has a circular inner and outer circumference, but other shapes, such as for instance a polygon, are also possible. In FIG. 1, the ring element (103) has an inner diameter of approximately 1.6 m. However, the invention is not limited to this size, embodiments of larger as well as smaller inner diameters being possible.
[0076] In FIG. 1, the outer circumference of the stator ring (100) is formed by boundary elements (102). In the embodiment of FIG. 1, there are several boundary elements (102) linked to each other, but an embodiment comprising one boundary element (102) forming the entire outer circumference is also possible. In the embodiment of FIG. 1 and FIG. 2, the distance between the inner diameter of the ring element (103) and the outer circumference of the stator ring formed by the boundary elements (102), measured along the radial direction, is approximately 10 cm. However, the invention is not limited to this size, embodiments of a larger as well as smaller size being possible.
[0077] The stator elements (101) are situated between the ring element (103) and the outer circumference formed by the boundary elements (102). Typically, the stator elements (101) are evenly distributed along the circumference of the stator ring, with equal distance between two adjacent stator elements (101) measured in tangential sense. In the embodiment of FIG. 1, 92 stator elements (101) are positioned along the circumference of the stator ring (100). However, a different number of stator elements (101) higher or lower than 92, is also possible. A stator element (101) comprises a core (200) and a coil (201), as can also be seen in FIG. 4. The core (200) consists of ferromagnetic material such as Fe or Ni or FeNi alloys. Preferably, the core is constructed in a laminated fashion, comprising a plurality of layers of ferromagnetic material. In the representation of the core (200) in FIG. 4 and in the other figures, only a limited number of layers of ferromagnetic material is shown for sake of clarity of the representation. In reality, a much larger number of layers will typically be present. The ferromagnetic core (200) is for instance surrounded by a layer of electrically insulating material. At least one electrically conductive winding or coil (201), typically a copper winding, is wound around the core (200). Optionally, the coil (201) is in turn surrounded by a layer of electrically insulating material. During operation of the generator, an electric current is induced in each of the coils (201). The coils (201) are connected to each other, for instance via one or more rings. A wire or rod of electrically conductive material is for instance connected to this ring/those rings, for taking the generated electric current to the outside environment of the stator (100).
[0078] The stator elements (101) are anchored in a filling material (105) that has cured after manufacturing the stator (100). The filling material (105) preferably conducts heat but does not conduct electricity. The filling material (105) for instance is an artificial resin such as polyester, epoxy, . . . . Optionally, it is reinforced by for instance fiber glass or carbon fibers.
[0079] In FIG. 1 and FIG. 2, the outer circumference of the stator ring (101) is formed by boundary elements (102) that are linked to each other. The outer circumference has the shape of a circle or polygon. In the embodiment of FIG. 1 and FIG. 2, all boundary elements (102) are also cooling elements (600), which means that they are suitable for conducting heat. This is advantageous in obtaining a proper discharge of heat when the generator is operative, and in limiting the number of parts. However, the invention is not limited to such an embodiment, and embodiments in which the boundary elements consist of cooling elements on the one hand and elements without a cooling function on the other hand, are also possible. In such an embodiment for instance the outer circumference of the stator (100) is built up from a sequence in which a cooling element is alternated with a boundary element without a cooling function.
[0080] The boundary elements (102) functioning as cooling elements (600) are made of a non-ferromagnetic material having a proper thermal conductivity, for instance Al, an Al alloy, copper or a copper alloy. In FIG. 2, the cooling elements (600) have elongated components (601) extending between the stator elements (101). Preferably, an elongated component (601) is situated between each pair of stator elements (101). This ensures that during operation of the generator, heat is discharged from locations in the vicinity of where the heat is produced. On the one hand, the distance between an elongated component (601) and a stator element (101) is small to ensure a proper thermal contact, but on the other hand large enough to permit an easy positioning of a stator element (101) without the risk of damaging the insulating exterior layer of the stator element (101). Furthermore, the cooling elements (600) in FIG. 2 have elongated components (602) that are externally oriented relative to the outer circumference of the stator (100). They permit increasing the contact surface with the ambient air, so that during operation of the generator an improved cooling is achieved than would be the case if externally oriented elongated components (602) were absent. The advantage of the embodiment of FIG. 2, including internally and externally oriented elongated components (601, 602, respectively) is that no cooling by means of a coolant circulating in the interior or exterior of the stator (100) needs to be used. However, an embodiment in which there are no externally or no internally oriented elongated components (601, 602, respectively), and use is made of a coolant circulating in the interior or exterior of the stator (100) is also possible.
[0081] FIG. 6 shows a 3D-reproduction and a cross-section perpendicular to the axis of rotation of a cooling element (600) according to an embodiment. This is the embodiment of the cooling element (600) as can also be seen in FIG. 1 and FIG. 2. In this embodiment, a cooling element (600) has four internally oriented elongated components (601) and twelve externally oriented elongated components (602). In FIG. 2 it can be seen how three stator elements (101) have been placed between the three respective pairs of internally oriented elongated components (601). The cooling elements (600) are linked together to form the outer circumference of the stator (100). In the embodiment of FIG. 1, FIG. 2 and FIG. 6, use is then made of a snap system, permitting an outer end (603) to be snapped into an outer end (604) of an adjacent cooling element (102). A similar system can be used for connecting boundary elements (102) without a cooling function to each other, or connecting boundary elements (102) without cooling function to cooling elements (600). Other ways of connecting boundary elements (102) with or without cooling function are also possible, such as gluing, welding or a mechanical connection. To conclude with, FIG. 6 shows how a connection (605) between two externally oriented elongated components (602) permits forming fixing points, with which the stator (100) can be secured. The advantage of this is that no extra components are needed to form such fixing points.
[0082] FIG. 5 shows another embodiment of a cooling element (500). In this embodiment the cooling element (500) comprises three externally oriented elongated components (502) and one internally oriented elongated component (501). FIG. 3 shows how within the stator (100) each time one stator element (101) is situated next to an internally oriented elongated component (501). In this figure, the cooling elements (500) are linked to one another by a snapping operation using the outer ends (503) and (504).
[0083] When manufacturing the stator (100), a cooling element (600) or (500) is produced as an integral part. The cross-sections shown in FIG. 6 and FIG. 5 permit producing the cooling element (102, 300) by means of a simple production technique for which standard machines are available. The production of a cooling element (500, 600) for instance takes place by means of an extrusion process, for instance Al-extrusion or by means of 3D-printing.
[0084] FIG. 7 shows yet another embodiment of a cooling element (700). When using a cooling element (700) within a stator (100), there is only one cooling element that also serves as single boundary element. The cooling element (700) consists of a ring (703) on which internally oriented elongated components (701) and externally oriented elongated components (702) are situated. Preferably, the ring (703) and the elongated components (701, 702) form one unity, but a mechanical anchoring of the components (701) and/or (702) on the ring (703) is also possible.
[0085] Preferably, a cooling element (500, 600, 700) is manufactured as one unity, in a heat conducting material such as Al or an Al alloy. That way, there is not a single interruption in the path that heat to be discharged needs to follow from an internally oriented elongated component (501, 601, 702) towards an externally oriented elongated component (500, 600, 701). This permits optimal conduction of heat and therefore optimal discharge of heat during operation of the generator. The cross-section perpendicular to the axis of rotation of the elongated components (501, 502, 601, 602, 701, 702) can have various shapes, such as rectangular or narrowing towards the tip. Optionally, the cross-section along the axis of rotation of an internally oriented elongated component (501, 601, 702) does not integrally consist of material, but interruptions have been made in it, for instance in the form of slits (505, 606, 704). In the embodiment in FIG. 5, FIG. 6 and FIG. 7, the slits (505, 606, 704) are made perpendicular to the axis of rotation and there are several slits (505, 606, 704) along the height, measured along the axis of rotation, of an elongated component (501, 601, 701). Other shapes and directions of interruptions made in an internally oriented elongated component (501, 601, 702) are also possible. Providing interruptions or slits (505, 606, 704) prevents eddy currents from arising which adversely affect the efficiency of the generator. The slits (505, 606, 704) are for instance made after the production of a cooling element (500, 600, 700 respectively), for instance by sawing or cutting, or are already provided during production of the cooling element (500, 600, 700) for instance by 3D-printing.
[0086] FIG. 8a and FIG. 8b show a cross-section of the stator ring (100) along the axis of rotation, according to an embodiment of the invention. It shows a position jig (801), which in the manufacturing of the stator (100) is poured on as permanent material. In the embodiment of FIG. 8a and FIG. 8b, the ring element (103), the cores (200) and the boundary elements (102) have surfaces that are perpendicular to the axis of rotation, and that are all situated perfectly in one plane. The position jig (801) is also situated in this very same plane. A perfectly flat stator wall perpendicular to the axis of rotation is then obtained. Small pits, if any, arising in the filling material (105) may be permissible as long as the stator elements (101) are properly anchored in the filling material (105). In FIG. 8a and FIG. 8b, the ring element (103) is the outer ring of a radial bearing. FIG. 8b also shows that the height, measured along the axis of rotation, of the inner ring (104) of this bearing is slightly larger than the height, measured along the axis of rotation, of the outer ring (103). Once a rotor (1000) has been mounted on the inner ring (104), this difference in height will form the air gap (800) between the cores (200) and the magnets (1003). The advantage thereof is that a very narrow air gap (800) can be realized, the thickness of which, measured along the axis of rotation, can be guaranteed at any location. In an alternative embodiment, both bearing rings (103, 104) are equally high, and the difference in height, measured along the axis of rotation, is obtained by mounting an extra annular element on the inner ring of the bearing. In the embodiment of FIG. 8b, the thickness, measured along the axis of rotation, of the air gap (800) is approximately 1 mm, and the thickness, measured along the axis of rotation, of the stator ring (100) is approximately 14 cm. Larger or smaller thicknesses are possible, however. Optionally, the optimal thickness of the air gap (800) can be defined in function of the degree of deflection of rotor (1000) and/or stator (100) which arises as a result of magnetic forces during operation of the generator. This can be determined through simulations or by experiments.
[0087] FIG. 9a shows an embodiment of the method (900) for manufacturing a stator (100) according to the invention. Steps referred to in a text box with broken lines indicate a step that is optional or specific to this embodiment. FIG. 9a also indicates a specific sequence of the steps to be carried out. However, the invention is not limited to this embodiment, and other sequences of the steps to be carried out, particularly as regards the positioning of the various elements, is possible. FIG. 9b shows a cross-section along the axis of rotation of a table (920) used in the manufacturing of the stator (100). FIG. 9b also shows the stator (100) after the steps referred to in FIG. 9a have been carried out.
[0088] In the embodiment of FIG. 9a, a surface is provided in a first step (901), which surface comprises one or more flat support surfaces (921, 922) perpendicular to the axis of rotation. Optionally, this is providing (905) a perfectly flat table (920), consisting of one flat surface (921) in which a circular recess (922) is provided. Referring to the embodiment of FIG. 8b, in which the ring element (103) is the outer ring of a radial bearing, and the inner ring (104) has a larger height, measured along the axis of rotation, the circular recess (922) is intended for receiving the inner ring (104) of the bearing. The perfectly flat surface (921) is intended for receiving the stator elements (101), the boundary elements (102) and the ring element (103) for positioning. In another embodiment the flat table comprises several shallow recesses serving as support surfaces, intended for receiving the stator elements (101 and/or ring element (103) and/or boundary elements (102). The surface (921) has to be treated such as not to bond to the filling material (105) with which everything will be poured on. Optionally, a piece of paper or foil can be used for that purpose.
[0089] In the embodiment of FIG. 9a, in which use is made of an entirely flat table having a circular recess, first one or several position jigs (801) are positioned on the perfectly even surface, as indicated in step (906). A jig for instance consists of several pieces that snap into each other and optionally are glued together using a thin soluble glue, or it can be made as one unity. The position jig (801) comprises recesses corresponding to the shape of the elements to be positioned. A position jig (801) is for instance made from plastic through 3D-printing, or manufactured by means of a technique such as cutting, or punching, etc. The jig (801) will be poured on as permanent material. A position jig (801) serves to indicate where the elements have to be positioned, and to keep these elements in their right places more properly. The recesses in the position jig (801) may optionally be provided with a small legs and small bumps, so that when an element does not have the exact dimensions, the recesses yield slightly flexibly.
[0090] In FIG. 9a, the individual stator elements (101) and the one or more boundary elements (102) are positioned in a next step (902). Referring to the embodiment of FIG. 2 or FIG. 3, this step relates to the positioning (907) of individual cooling elements (500, 600) on the one hand and the positioning (908) of individual stator elements (101) on the other hand. For instance, all individual cooling elements (500, 600) are placed first, the position being accurately determined by the position jig (801). The individual cooling elements (500, 600) can be linked together beforehand, using the outer ends (503, 504, and 603, 604, respectively) or this can be done during positioning. In the latter case, for instance a cooling element (500, 600) is placed and snapped to an already positioned cooling element (500, 600). Subsequently, all individual stator elements (101) are positioned, once again using the position jig (801). In an alternative embodiment, the individual cooling elements (500, 600) are placed alternating with the individual stator elements (101), which could optionally permit a less complex positioning of the stator elements (101) between the internally oriented elongated components (501, 601). After positioning the stator elements (101), the coils (201) are connected in step (909), for instance by soldering them to one or more rings, and connecting a conductor thereto which is taken to the outside via recesses in the cooling elements (500, 600). In the embodiment of FIG. 9a, this takes place even before the rings of the radial bearing (103, 104) are positioned. The advantage thereof is that the stator elements (101) are properly accessible.
[0091] In the embodiment of FIG. 9a, the radial bearing, including inner ring (104) and outer ring (103), is subsequently positioned in steps (903) and (910). For instance, the inner ring (104) is first placed in the circular recess in the table, and subsequently the outer ring is positioned on the flat table.
[0092] In the embodiment of FIG. 9a, in step (911) a jig is also placed on top of the positioned elements to keep everything precisely in its place, but this not a necessity. Optionally, a lid that does not bond to the resin can be placed on top of it, to keep the positioned elements in their correct places. Subsequently, the empty spaces between the ring element (103), the boundary elements (102) and the stator elements (101) are filled with a filling material (105) in step (904). The filling material (105) preferably conducts heat but does not conduct electricity. The filling material (105) for instance is an artificial resin such as polyester, epoxy, . . . . Optionally prior to filling, for instance glass fibers or carbon fibers can be placed in the empty spaces between the stator elements (101). Subsequently the unit is poured on or a vacuum is applied thereon using filling material (105). Preferably, no air bubbles are left in the filling material (105). After the filling material (105) has cured, a flat stator disk (100) is obtained, wherein the filling material (105) ensures bonding to the outer bearing ring (103) and wherein the stator elements (101) are firmly anchored in the filling material (105). This flat stator disk (100) can be seen in FIG. 9b.
[0093] FIG. 10 shows a 3D-reproduction of a rotor (1000) according to an embodiment of the invention. Typically, the rotor (1000) is a disk of a specific thickness, measured along the axis of rotation, in the center of which there is an aperture intended for the shaft of the machine. The rotor ring (1000) forms an integral part, wherein the magnets (1003) are anchored in a filling material (1004). Typically, the inner circumference and the outer circumference of the rotor ring (1000) have a circular cross-section perpendicular to the axis of rotation, but other shapes, such as for instance a polygon, are also possible.
[0094] Typically, the magnets (1003) are evenly distributed along the circumference of the rotor ring, with equal distance between two adjacent magnets (1003) measured in tangential sense. In the embodiment of FIG. 10, 92 magnets (1003) are positioned along the circumference of the rotor ring (1000). However, a different number of magnets (1003) higher or lower than 92, is also possible. The magnets (1003) typically are permanent magnets, but another type, such as for instance electromagnets, is also possible. In the embodiment of FIG. 10, a magnet (1003) in radial sense consists of one unit. However it is also possible that a magnet (1003) in radial sense consists of several separate units. The cross-section of a magnet (1003) perpendicular to the axis or rotation may have several shapes, such as rectangular, or narrowing towards an outer end.
[0095] FIG. 12a and FIG. 12b show a cross-section along the axis of rotation of a rotor (1000) according to an embodiment. It shows a position jig (1200), which in the manufacturing of the rotor (1000) is poured on as permanent material. FIG. 11 shows a cross-section perpendicular to the axis of rotation of a rotor (1000) according to an embodiment. In the embodiment of FIG. 11, FIG. 12a and FIG. 12b, the rotor (1000) comprises ferromagnetic material (1100). Any material that can easily be magnetically polarized can be used as ferromagnetic material (1100), such as transformer steel, iron-nickel alloys, alloys of iron and silicon, etc. FIG. 12a and FIG. 12b show that a magnet (1003) does not continue along the full thickness, measured along the axis of rotation, of the rotor ring, but that a part of this thickness is taken up by ferromagnetic material (1100). In the embodiment of FIG. 11, FIG. 12a and FIG. 12b, the ferromagnetic material (1100) has the shape of a helical ribbon, wherein the ribbon makes several revolutions along the circumference of the rotor ring (1000), and the various circular strips contact each other and optionally are glued together. The advantage thereof is that in the manufacturing of the rotor, the ferromagnetic material (1100) can easily be unrolled like a continuous ribbon. Other embodiments are possible however, wherein for instance use is made of concentric circles of ferromagnetic material that abut each other, or of one single broader strip of ferromagnetic material. Preferably, in the radial sense the location where the ferromagnetic material (1100) is situated, is determined by the dimensions of the magnets (1003) in radial sense. The advantage thereof is that the ferromagnetic material (1100) contributes to closing the magnetic flux lines, but for the remaining part the rotor (1000) may consist of a more lightweight material.
[0096] The magnets (1003) and the ferromagnetic material (1100) are anchored in an electrically insulating filling material (1004), for instance an artificial resin such as polyester, epoxy, . . . , which has cured after manufacturing the rotor (1000). Optionally, it has been reinforced by for instance fiber glass or carbon fibers. Optionally, the magnets (1003) have a longitudinal notch (1005) to enhance the bonding in the filling material (1004).
[0097] In FIG. 12b it can be seen that the rotor ring (1000) has a surface, which includes the magnets (1003) and the position jig (1200) in there, which is perpendicular to the axis of rotation, and is completely flat. This makes it possible to realize a constant narrow air gap (800) after mounting stator (100) and rotor (1000). The thickness, measured along the axis of rotation, of the rotor disk (1000) on the one hand is determined by the height, measured along the axis of rotation, of the magnets (1003) and the ferromagnetic material (1100), and on the other hand by the required rigidity and strength of the rotor (1000). The required strength and rigidity of the rotor (1000) is determined by the magnitude of the forces arising during the operation of the generator, which in turn depends on the capacity level of the generator. In the embodiment of FIG. 12b, the thickness, measured along the axis of rotation, of the rotor ring (1000) is approximately 5 cm. However, embodiments having another thickness, larger or smaller than 5 cm, are also possible.
[0098] FIG. 13a shows the method (1300) for manufacturing a rotor (1000) according to an embodiment of the invention. Steps referred to in a text box with broken lines indicate a step that is optional or specific to this embodiment. FIG. 13a also indicates a specific sequence of the steps to be carried out. However, the invention is not limited to this embodiment, and other sequences of the steps to be carried out, particularly as regards the positioning of the various elements, is possible. FIG. 13b shows the cross-section along the axis of rotation of a table (1321) and two ring elements (1001, 1002) which are used in the manufacturing of the rotor (1000). FIG. 13b also shows the rotor (1000) after the steps referred to in FIG. 13a have been carried out.
[0099] In the embodiment of FIG. 13a, a surface is provided in a first step (1301), which surface comprises one or more flat support surfaces (1320) perpendicular to the axis of rotation. In the embodiment of FIG. 13a, this is providing (1305) a fully flat, perfectly even table (1321). In another possible embodiment, the flat table comprises several shallow recesses, intended for receiving the magnets (1003). Optionally, the surface (1320) is made slightly magnetic or sticky by an easily soluble adhesive. Optionally, a film or paper is used to prevent that the surface (1320) does not bond to the filling material (1004) with which everything will be poured on.
[0100] In the embodiment of FIG. 13a, first one or more position jigs (1200) are positioned on the completely even surface (1320) in step (1306). A jig for instance consists of several pieces that snap into each other and optionally are glued together using a thin soluble glue, or it can be formed as one unity. The position jig (1200) comprises recesses corresponding to the shape of the elements to be positioned. A position jig (1200) is for instance made from plastic through 3D-printing, or manufactured by means of a technique such as cutting, or punching, etc. The jig (1200) will be poured on as permanent material. A position jig (1200) serves to indicate where the elements have to be positioned, and to keep these elements in their right places more properly.
[0101] In the embodiment of FIG. 13a, the magnets (1003) are positioned in a next step (1302) by means of the position jig(s) (1200). Subsequently, in step (1307), the ferromagnetic material (1100) is arranged, for instance in the form of a helix of ferromagnetic ribbon. It is also possible to first mount, for instance glue, the magnets (1003) by means of a jig to a helix of ferromagnetic material (1100) and subsequently turn this unit around and position it on the even table.
[0102] In the embodiment of FIG. 13a, in a next step (1303), two annular elements (1001, 1002, respectively) are positioned for the inner circumference and for the outer circumference, respectively. The position jig can then be made use of The height, measured along the axis of rotation, of the annular elements (1001, 1002) determines the thickness, measured along the axis of rotation, of the rotor (1000). The annular elements (1001, 1002) are removed again once the filling material (1004) has cured.
[0103] In the embodiment of FIG. 13a, in a last step (1304), the empty spaces between the first annular element (1001), the magnets (1003) and the second annular element (1002) is filled with a filling material (1004). The filling material (1004) for instance is an artificial resin such as polyester, epoxy, . . . . Optionally prior to filling, for instance glass fibers or carbon fibers can be placed in the empty spaces between the magnets (1003). Subsequently the unit is poured on or a vacuum is applied thereon using filling material (1004). Once the filling material (1004) has cured, a flat rotor disk (1000) is obtained, wherein the filling material (1004) ensures bonding to the annular elements (1001, 1002), and wherein the magnets (1003) and the ferromagnetic material (1100) are firmly anchored in the filling material (1004). This flat rotor disk (1000) can be seen in FIG. 13b.
[0104] FIG. 14 and FIG. 15 show a 3D-reproduction and a cross-section along the axis of rotation of two rotors mounted on a stator according to an embodiment of the invention. A rotor (1000) is mounted on either side of a stator (100). The side of a rotor (1000) showing the surface of the magnets (1003) faces the stator (100). The radial position of the magnets (1003) on the one hand and of the stator elements (101) on the other hand is such that a magnetic flux is able to run from a magnet (1003) on the one rotor (1000), through a core (200) on the stator (100), to a magnet (1003) on the other rotor (1000). In the embodiments of FIG. 1 and FIG. 10, a stator (100) and a rotor (1000), respectively, are shown, wherein the stator (100) has 92 stator elements (101) and the rotor (1000) has 92 magnets (1003). However, the invention is not limited to a generator in which the number of stator elements (101) equals the number of magnets (1003). It is also possible, for instance, that the number of magnets (1003) exceeds the number of stator elements (101), for instance in a ratio of four over three, which is advantageous in a three-phase system.
[0105] The flat rotor ring (1000) is attached to the inner ring (104) of a radial bearing. The attachment may for instance be made by means of screws, glue or another suitable technique. In FIG. 14 and FIG. 15, the ring element (103) is the outer ring of a radial bearing, which has a height, measured along the axis of rotation, that is slightly smaller than the height of the inner ring (104) of the bearing. The difference in height between the inner ring (104) and the outer ring (103) of the bearing defines the thickness of the air gap (800) between stator (100) and rotor (1000). As a consequence, when the generator is operative, the magnets (1003) will rotate at the exact distance of the stator elements (101), on either side of the stator (100).
[0106] FIG. 16 and FIG. 18 show a 3D-reproduction of a wind turbine (1600), considered along the front side and rear side, respectively, according to an embodiment of the invention. FIG. 17 shows a front view of this embodiment of the wind turbine (1600), and FIG. 19 shows a cross-section along the axis of rotation. The wind turbine (1600) comprises an axial flux generator having a stator (100) and two rotors (1000). The shaft (1603) is fixedly mounted on a base. That means that the shaft (1603), arranged coaxial to the central axis of rotation of the vanes of the wind turbine, does not rotate along with the blades or vanes of the wind turbine, but constitutes a stationary bearing point for these vanes. The base is not shown in the figures, however, this base may for instance be arranged so as to be rotatable about a substantially vertical axis on top of a tower of the wind turbine, so that the substantially horizontal central axis of rotation of the blade can be positioned optimally relative to the wind direction. The blades (1601) are mounted on the fixed shaft (1603) by means of a bearing (1604). The stator (100) is fixedly mounted on the fixed shaft (1603). Use is made of the fixing points (605) which are provided in the boundary elements (600), and of bolts that are arranged through the holes (1606) so that, the stator is mounted, via the arms (1607), fixedly to the shaft (1603). It is clear that the rotors (1000) as described above are bearing mounted on the stator (100). According to the embodiment shown, cables (1602) have been mounted, wherein one outer end is attached to a blade (1601) and the other outer end is attached to a fixing point (1605). A fixing point (1605) is situated on a part that is fixedly connected to the rotor (1000) at the opposite side of the arms (1607). It is clear that each blade (1601) comprises two cables (1602) extending on either side of the longitudinal axis of the blade in a plane that is substantially transverse to the central axis of rotation of the rotor of the wind turbine including the blades, and therefore the axial flux generator as well. That way the rotor (1000) is directly driven by the blades or vanes (1601), without using a rotating shaft. In other words: at least a part of the drive torque generated by the blade of the wind turbine is directly transferred via the cables to the rotor (1000) of the axial flux generator that is situated at the side facing the vanes. This makes it possible to avoid the use of a heavy bearing mounting and a turbine casing. In other words: the drive torque exchanged between the blades (1601) and the axial flux generator via the bearing (1604) is reduced as a result. The cables (1602) also serve as tension cables, permitting the blades (1601) to be executed more lightweight. In the embodiment of FIG. 16 and FIG. 17, two fixing points (1605) per blade (1601) are provided. This ensures an evenly distributed load, so that the whole can be executed more lightweight. It is clear that according to the embodiment shown, a suitable plurality of spokes (1608) is arranged which also connect the rotor (1000) and the fixing points (1605) to the bearing (1604), and that, as at least a part of the drive torque is transferred via the cables, those spokes can then be executed more lightweight. Furthermore, it is clear that according to an alternative embodiment that is not shown, such spokes (1608) can be dispensed with, the drive torque being fully transferred to the rotor of the axial flux machine by the cables (1602).
[0107] In this context, the term “perpendicular to” a reference direction is defined as at an angle of 90° to said reference direction, with a tolerance of plus or minus 10°, preferably 5°, more preferably 3°. In this context, the term “flat surface” or “flat support surface” is defined as a perfectly even and level surface wherein any irregularities, bulges or pits in the surface have a dimension of at the most 10% of the thickness of the air gap, preferably 5%, or more preferably 3%.
[0108] Although the present invention was illustrated on the basis of specific embodiments, it will be clear to the expert that the invention is not limited to the details of the above illustrative embodiments, and that the present invention can be configured including various changes and amendments without departing from the scope of the invention. The present embodiments therefore have to be considered illustrative in all aspects and not restrictive, wherein the scope of the invention is described by the attached claims and not by the above description, and all changes that fall within the meaning and scope of the claims, will therefore be included herein. In other words: it is taken as starting point that all changes, variations or equivalents that fall within the scope of the underlying basic principles and of which the essential characteristics are claimed in this patent application, are included. Moreover, the reader of this patent application will understand that the words “comprising” or “comprises” do not preclude other elements or steps, that the word “a/an” does not preclude the plural. Any references in the claims should not be taken as a limitation of the claims in question. The terms “first”, “second”, “third”, “a”, “b”, “c” and the like, when used in the description or in the claims are used to make a difference between similar elements or steps and do not necessarily describe a sequence or chronological order. Likewise, the terms “upper side”, “lower side”, “over”, “under” and the like are used for the sake of the description and they do not necessarily refer to relative positions. It should be understood that under the right circumstances, those terms are interchangeable and that embodiments of the invention are capable of functioning according to the present invention in different sequences or orientations than those described or illustrated in the above.
