TECHNICAL FIELD

The present invention generally relates to electrical machinery.

BACKGROUND ART

This section illustrates useful background information without admission of any technique described herein representative of the state of the art.

In electrical machinery, the stator and rotor wheel structures must work together to resist the large forces acting upon their facing surfaces. Since the air gap must be kept small to optimize efficiency, the structures must hold radial deformations to an absolute minimum. Furthermore, dynamic performance is important. Particularly, as a generator diameter becomes larger, dynamic response and the mass of the structures become more of an issue.

SUMMARY According to a first example aspect of the invention there is provided a wheel of an electrical machine, comprising:

a hub and a rim connected by spokes,

the rim being formed by layered sheet metal elements assembled together. The wheel may be, for example, a rotor or stator wheel.

In certain example embodiments, the layered sheet metal elements comprise overlapping parts so that a first layered sheet metal element contains a part extending in between an adjacent layered sheet metal element.

In certain example embodiments, the layered sheet metal elements are assembled together forming a staggered structure. In certain example embodiments, an individual layered sheet metal element comprises a plurality of sheet metal layers attached together forming at least one spoke and a section of the rim. In certain example embodiments, the number of spokes formed by the individual sheet metal element is two.

In certain example embodiments, the wheel comprises a structure configured to minimize radial deformation of the wheel.

In certain example embodiments, the wheel uses a slanted spoke and rim architecture to provide good static structural performance with minimum weight. In certain example embodiments, the spokes are slanted and they come out from the hub tangentially.

In certain example embodiments, layered sheet metal elements are used to form the spokes and rim of wheel faces.

In certain example embodiments, the layered sheet metal elements are made of steel.

In certain example embodiments, the layered (stacked) sheet steel elements, when bound, establish structural integrity with an increase in structural damping perpendicular to the stack due to friction between the layers. With use of the layered sheet metal elements, substantial spoke-and-rim wheel structures can be built up without welding together overly thick steel elements.

According to a second example aspect of the invention, there is provided an electrical machine comprising the wheel of the first aspect or of any of its embodiments.

According to a third example aspect of the invention, there is provided an electrical machine comprising a first wheel attached to a hub by spokes and a second wheel attached to the hub by spokes, wherein at least one of said first and second wheels comprise a rim and spokes formed by layered sheet metal elements assembled together, and wherein the second wheel is placed around the first wheel.

In certain example embodiments, both of said first and second wheels comprise a rim and spokes formed by layered sheet metal elements assembled together.

The electrical machine may be, for example, a generator or an electrical motor.

Different non-binding example aspects and embodiments of the present invention have been illustrated in the foregoing. The embodiments in the foregoing are used merely to explain selected aspects or steps that may be utilized in implementations of the present invention. Some embodiments may be presented only with reference to certain example aspects of the invention. It should be appreciated that corresponding embodiments may apply to other example aspects as well.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments of the invention will be described with reference to the accompanying drawings, in which: shows a view of a wheel of an electrical machine in accordance with an example embodiment;

Figs. 2-4 show certain parts of the wheel of Fig. 1 ;

Fig. 5 shows a rim assembly in accordance with an example embodiment; Figs. 6-7 show certain structural details of the wheel of Fig. 1 ;

Fig. 8 shows structural deformations in an example embodiment; and

Fig. 9 shows an electrical machine in accordance with an example embodiment.

DETAILED DESCRIPTION

In the following description, like reference signs denote like elements or steps. Fig. 1 shows a view of a wheel of an electrical machine, for example an electrical motor or generator, in accordance with an example embodiment. The wheel 100 comprises a hub 105 and a rim 1 15 connected by spokes 1 1 1 . The rim 1 15 is formed by layered sheet metal elements 1 10, 1 10' assembled together.

The sheet metal elements 1 10, 1 10' are stacked to form a wheel face 120 with spokes 1 1 1 and rim 1 15. A pair of wheel faces 120 is attached to the hub 105 (one on each side of a hub plate, such as an inner hub plate, or similar) resulting in a wheel structure side 130. A pair of wheel structure sides 130, 130' is spaced apart at an interval defined by the hub 105. A circular array of crossing tubes 140 connects the two wheel structure sides 130, 130' at the rim 1 15 to form a complete lightweight wheel structure (the crossing tubes 140 also keep the layered sheet metal elements 1 10, 1 10' in position). The structure is stiffened axially with internal cross bracing (bracing straps 150) extending between the wheel structure sides 130, 130'.

Spacers (not shown in Fig. 1 ) sit between the pair of wheel faces 120 of the wheel structure side 130 (and between the pair of wheel faces of the wheel structure side 130', respectively) in line with the spokes 1 1 1 to maintain the spacing established by the hub (or hub plate) 105. The spacers may be, for example, of polymer material (such as high density polyethylene) to introduce structural damping in the axial direction of the wheel 100. Figs. 2-4 show side views of certain parts of the wheel 100.

Fig. 2 shows a side view of the hub 105 comprising attachment points 1051 (e.g., holes) for attaching the layered sheet metal elements 1 10, 1 10' to the hub 105. Fig. 3 shows a side view of the layered sheet metal element 1 10 (or 1 10', respectively). The element 1 10 forms a section of the entire wheel 100. The layered sheet metal element 110 comprises a portion of the rim 115 (hereinafter denoted as rim portion 115) and at least one spoke 111. In this example embodiment, the number of spokes 111, 111' comprised by the element 110 is typically two. The two spokes 111, 111' begin at a common point in the end of the element 110 pointing towards the hub 105. The spokes 111, 111' extend separately (divided by an angle as in letter "V") to meet the rim portion 115 at respective points thus forming a triangle there between (defined by the adjacent spokes 111, 111' and the rim portion 115). The element 110 comprises attachment points 1101 (e.g., holes) in the end of the element 110 pointing towards the hub 105 for attaching the element 110 to the hub. The element 110 further comprises attachment points 1102 (e.g., holes) in the rim portion 115 for attaching the crossing tubes 140 to the rim portion 115. The way of attaching parts of the wheel 100 together depends on the implementation. For example bolting, riveting, tying, welding, and/or clinching can be used.

Fig.4 shows a side view of a wheel face 120. The wheel structure therein uses a spoked-wheel architecture. However, the spokes 111, 111 ' do not radiate outward normal to the hub 105. Instead, they are slanted and come out from the hub 105 tangentially. This orientation enables the wheel structure to provide good static structural performance with very light weight when the wheel rim is subjected to both tangential and radial forces.

Fig. 5 shows a rim assembly in accordance with an example embodiment. As mentioned in the preceding, the described wheel 100 comprises layered sheet metal elements 110, 110' assembled (or attached) together. The layering of the sheet metal elements introduces damping to the structure, especially in the axial direction.

The layered sheet metal elements may form both the rim 115 and the spokes 111, 111', or in certain example embodiments, the (outer) rim 115 only. The elements 1 10, 1 10' form overlapping segments so that the element 1 10' contains a part extending in between the adjacent element 1 10. Each layered sheet metal element 1 10, 1 10' is formed by stacked sheet metal layers (such as sheet steel layers). The layers of the adjacent elements 1 10, 1 10' attach together in a staggered manner at the rim 1 15. Friction between layers establishes structural integrity. The interaction between layers and the resulting increase in damping normal to the stack offers improved dynamic performance.

In the example of Fig. 5 the number of layers in the elements 1 10, 1 10' is five. The basic interface between the adjacent elements 1 10 and 1 10' is denoted as "A" and an extended interface located deeper within the area of element 1 10 as "B". The first, third and fifth layer of the elements 1 10 and 1 10' meet at the interface A, whereas the second and fourth layer of the element 1 10' extend in between the first, third and fifth layer of element 1 10 till they meet the second and fourth layer of element 1 10 at the extended interface B.

Figs. 6 and 7 show certain structural details of the disclosed wheel 100 in an example embodiment. Fig. 6 shows the spokes 1 1 1 , 1 1 1 ' made of sheet metal layers attached to both sides of a respective hub plate 105 by bolts 670.

Fig. 7 shows spacers 780 placed in between the wheel faces 120 of a first wheel structure side 130 as well as between the wheel faces 120' of the other wheel structure side 130'.

Fig. 8 shows structural deformations in the type of wheel structure with slanted spokes as described in the preceding. Applying radial magnetic forces causes the outer rim of the wheel structure to deform outward. Applying tangential forces pulls the rim back into position. In the same way, slanting the spokes of the outer rotor away from the tangential forces pulls its outer diameter outward in opposition to the inward pull of the magnetic forces, which again results in less overall radial deformation. Spoke deformations due to radial and tangential forces combine to yield a resultant with minimal radial displacement.

Fig. 9 shows an electrical machine in accordance with an example embodiment. The electrical machine 900 comprises a first wheel 901 attached to a hub 905 (e.g., to an inner hub plate) by spokes and a second wheel 902 attached to the hub 905 (e.g., to an outer hub plate) by spokes. The second wheel 902 is placed around the first wheel 901 . There is the required air gap in between. The first and second wheels are of the disclosed type. Accordingly, the first and second wheels comprise a rim and spokes formed by the layered sheet metal elements assembled together.

In certain other embodiments, one of the wheels is formed differently. It may, for example, not have the spoke-and-rim architecture at all, or the spokes and/or rim of that wheel need not be formed of layered sheet metal elements.

Various embodiments have been presented. It should be appreciated that in this document, words comprise, include and contain are each used as open-ended expressions with no intended exclusivity.

Without limiting the scope and interpretation of the patent claims, certain technical effects of one or more of the example embodiments disclosed herein are listed in the following: A technical effect is a lightweight layered sheet-steel wheel structure for rotor and stator use in low-speed electrical machinery. Another technical effect is that the deep structural welds that would normally be needed to build up a wheel structure of a large scale are not required with the layered sheet metal architecture. As a result, issues with fatigue cracking and failure at the welds over the life expectancy of the structure are eliminated and manufacturing costs are reduced. Another technical effect is increase in structural damping due to friction between the layered sheet metal elements that establishes structural integrity.

The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments of the invention a full and informative description of the best mode presently contemplated by the inventor for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented in the foregoing, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention.

Furthermore, some of the features of the afore-disclosed embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present invention, and not in limitation thereof. Hence, the scope of the invention is only restricted by the appended patent claims.