Machine with two co-axial rotors

Abstract

A machine having two co-axial and relatively rotatable rotors and a coaxial stator or housing with respect to which both rotors are rotatable is provided wherein two bearing arrangements mutually support the two rotors with respect to each other and with respect to the stator or housing. One of the bearing arrangements comprises multiple support bearings angularly spaced apart with respect to the axis of rotation of the rotors relative to the stator with the support bearings each having an axle or shaft that is fixed relative to one of the rotors or the stator. Each support bearing cooperates with a raceway provided on a concentric adjacent rotor or stator. The machine may be an electromechanical machine such as a wind turbine in which rotational movement of one of the rotors relative to the other and relative to the stator generates electrical energy.

Claims

1. A machine having two co-axial and relatively rotatable rotors and a coaxial stator or housing with respect to which both rotors are rotatable and wherein two bearing arrangements mutually support the two rotors with respect to each other and with respect to the stator or housing wherein one of the bearing arrangements comprises multiple support bearings angularly spaced apart with respect to the axis of rotation of the rotors relative to the stator with the support bearings each having an axle or shaft that is fixed relative to one of the rotors or the stator with each support bearing cooperating with a raceway provided on a concentric adjacent rotor or stator wherein a diameter of the raceway and angular arrangement of the support bearings is greater than the diameter of the other of the bearing arrangements.

2. A machine as claimed in claim 1 in which the support bearings each comprise an outer roller liner carried by a bearing body that in turn is carried by a bearing on the inside thereof.

3. A machine as claimed in claim 1 in which the bearing associated with each of the support bearings is a roller or a journal bearing.

4. A machine as claimed in claim 1 in which the support bearings each have a body supported either on an axle fixed relative to the rotor or stator or on a shaft rotatable relative to the rotor or stator.

5. A machine as claimed in claim 1 in which the other of the bearing arrangements is a conventional bearing coaxial with the axis of rotation of the rotors.

6. A machine as claimed in claim 1 in which the machine is an electromechanical machine in which rotational movement of one of the rotors relative to the other and relative to the stator generates electrical energy.

7. A machine as claimed in claim 1 in which the one rotor is an induction rotor driven by a wind turbine, with the other rotor being a freely rotating rotor having permanent magnets associated therewith so as to form a so-called split permanent magnet generator.

8. A machine as claimed in claim 1 in which the two rotors and stator are arranged one within the other to create radial flux coupling, in use.

9. A machine as claimed in claim 1 in which the two rotors and the stator are located immediately adjacent to each in the axial direction in order to create axial flux coupling.

10. A machine as claimed in claim 1 in which the support bearings are arranged to define, in cooperation with the raceway, an air gap between the two rotors or between a rotor and the stator as the case may be.

11. A machine as claimed in claim 1 in which the stator is either inside the two rotors or on the outside of the two rotors.

12. A wind turbine that embodies a machine as claimed in claim 1 in which the machine is in the form of an electrical generator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic elevation of an embodiment of the invention in which the stator is on the outside of the two rotors;

(3) FIG. 2 is a sectional side elevation taken along line II-II in FIG. 1;

(4) FIG. 3 is an enlarged section showing the arrangement of a support roller in more detail;

(5) FIG. 4 is a schematic elevation of an embodiment of the invention in which the stator is on the inside of the two rotors;

(6) FIG. 5 is a sectional side elevation taken along line V-V in FIG. 4;

(7) FIG. 6 is an enlarged section showing the arrangement of the support roller illustrated in FIG. 5 in more detail;

(8) FIG. 7 is a schematic sectional side elevation of the general arrangement illustrated in FIGS. 1 to 3 as applied to a wind turbine;

(9) FIG. 8 is a schematic front elevation thereof;

(10) FIG. 9 is a more detailed section showing the construction of a support roller therein;

(11) FIG. 10 is a schematic side elevation of an embodiment of the invention in which the two rotors and the stator are arranged for axial flux coupling between them; and,

(12) FIG. 11 is a schematic sectional side view of the embodiment of the invention illustrated in FIG. 10.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

(13) Referring firstly to the embodiment of the invention illustrated in FIGS. 1 to 3 of the drawings, a machine according to the invention is in the form of a split permanent magnet generator having an inner rotor (1) in the form of an induction rotor and a freely rotatable rotor (2) surrounding it with an air gap (3) between the two rotors. The freely rotatable rotor has a segmented construction with permanent magnets (4) associated therewith so as to form, with the surrounding stator (5) and the induction rotor (1), the split permanent magnet generator. The two rotors and stator are thus arranged one within the other to create a radial flux coupling and the rotors are rotatable with respect to each other and with respect to the stator as will become more apparent from the following.

(14) As may be appropriate, each of the rotors and stator may be made up of a series of laminates together with appropriate windings, as the case may be, in the usual way and their detailed construction is not further discussed herein as it is not of any relevance to the present invention.

(15) In this embodiment of the invention the induction rotor (1) is carried through a conventional type of bearing (6) by a tubular central support (7) that is fixed relative to the stator.

(16) However, as provided by this invention, the freely rotatable permanent magnet rotor (2) is carried by two axially spaced sets of multiple support rollers (8) that are angularly spaced about the periphery of the induction rotor relative to the common axis of rotation of the rotors. Each of the support rollers is carried on an axle or is fixed to a shaft (9) that is fixed relative to the permanent magnet rotor (2).

(17) The angular spacing of the support rollers in this embodiment of the invention is selected to be 30° but any other appropriate angular spacing could be employed as design detail may require, and especially according to the diameter of the circular array of support rollers; the size and specifications and adjustability of the support rollers themselves; and the desired air gap between the relatively rotatable rotors and the rotor and stator. Such an air gap is typically of the order of 5 mm.

(18) Radial and axial loading conditions will generally determine the bearing and roller selection. The roller size may depend on the air-gap requirement which is the clearance between the two rotating rotors. Rollers may be a combination of different materials layered to specific stress requirements. Roller interface with the raceways may be accomplished in various topologies, for example, a roller design with V-grooves.

(19) The two side edges (11) of the induction rotor are formed into segmented raceways on which the outer periphery of the support rollers rides in this embodiment of the invention.

(20) The bearing arrangements are thus composed of relatively simple and inexpensive bearings when compared to a large diameter bearing. The diameter of the raceway and angular arrangement of the support rollers, on the other hand, is substantially greater than the diameter of the conventional bearing (6).

(21) It is to be mentioned that, as shown in FIG. 9, each of the support rollers may comprise an outer roller liner (15) carried by a roller body (16) that in turn is carried by a roller bearing (17) on the inside thereof.

(22) Of course, it is within the scope of this invention that the stator be located on the inside of the rotors and such an arrangement is illustrated in FIGS. 4 to 6 of the drawings. In this instance the induction rotor (21) may be carried on a central tubular support (22) by way of a conventional bearing (23) with the permanent magnet rotor (24) being carried on a raceway (25) formed integral with the induction rotor by way of multiple rollers (26). The stator (27), in this embodiment of the invention, is on the inside of the rotors.

(23) Referring now to FIGS. 7 to 9 of the drawings, one application of an embodiment of the invention as illustrated in FIGS. 1 to 3 would be to a wind turbine. In this instance the wind turbine has a hub (31) from which the blades (32) extend radially and the hub is connected to drive the inner induction rotor (33) with the permanent magnet rotor (34) being located in between the induction rotor and the stator (35) as described with reference to FIGS. 1 to 3. The wind turbine could be of the general type described in our co-pending published patent application number WO 2012/017302.

(24) Referring now to FIGS. 10 and 11, the principles of the invention can also be applied to a machine in which there is axial flux coupling. In such an arrangement a generally horizontal first rotor (41) can be mounted rotatably relative to an axially adjacent stator (42) with the axially adjacent second rotor (43) being supported by the first rotor by way of an array of rollers (44). The rollers are illustrated as being inclined so as to cooperate with an inclined raceway (45) on the second rotor which can have the effect of centralizing the second rotor relative to the first. In this arrangement a single set of support rollers may be employed in the arrangement described.

(25) Application of the invention results in the utilization of smaller parts with accompanying improved maintainability. Use of the invention may be used to employ point of loading in order to minimize structural stiffness requirements hence structural material needs. The bearing support rollers may improve air-gap clearance management with a smaller air-gap deflection. The invention when applied to segmented rotor designs may yield reduced component size and thus also reduced shipping and maintenance time and cost. Smaller components or assemblies may also lead to cheaper machine manufacturing and the use of standard components.

(26) It will be understood that numerous variations may be made to the embodiments of the invention described above without departing from the scope hereof.