Flywheel

Abstract

The flywheel 1000 includes a plurality of disks 1002 arranged in a stack 1004, including first and second end disks at opposite ends of the stack 1004. Each disk 1002 includes a central region 1034 and a peripheral region 1032 disposed around the central region 1034. The peripheral region 1032 is adjacent to the periphery of the disk 1002. The flywheel also includes first and second plate members 1006 disposed at opposite ends of the stack 1004. The flywheel further includes a joining means 1030 that joins only a portion of each disk 1002 in the stack 1004 to a respective adjacent disk 1002. This includes joining adjacent peripheral regions 1032 of adjacent disks 1002 to each other. The joining means joins each of the first and second plate members 1006 to the first and second end disks of the stack 1004, respectively.

Description

[Technical field]

[0001] The present invention relates to flywheels, and particularly, but not exclusively, to flywheels for use in energy storage and / or distribution. [Background technology]

[0002] A flywheel is a device that includes a rotor assembly and an inertial element that can be used as a means to store kinetic energy. Most of the stored energy is stored in the inertial element that has a high moment of inertia relative to other elements of the rotor assembly, such as the electric machine and low friction bearing mountings.

[0003] Electric machines are commonly used to accelerate inertial elements to store energy or to decelerate inertial elements to release energy. An inertial element stores energy through its angular momentum: the faster it rotates, the more energy is stored, and energy storage is proportional to the square of the angular velocity.

[0004] In order to store high levels of energy (i.e., to have a large capacity for energy storage), the inertial elements must operate at very high peripheral speeds, typically above the speed of sound (measured in air under standard atmospheric conditions as opposed to conditions within the flywheel casing). Thus, the construction of the inertial elements in energy storage flywheels differs significantly from the construction of the inertial elements in flywheels designed for other applications.

[0005] For example, an extremely different application is to provide a flywheel attached to the crankshaft of an internal combustion engine to smooth out intermittent torque and prevent the engine from stalling. Flywheels used for such smoothing typically have a rotor peripheral speed of the order of tens of meters per second (relatively low energy capacity), whereas energy storage flywheels have a rotor peripheral speed of the order of hundreds of meters per second (relatively high energy capacity). This means that the flywheels in such smoothing applications are not subjected to the very high stresses that energy storage flywheel types must withstand. A further difference is that the energy storage flywheel can hold energy for seconds, minutes, or even hours, and then distribute the energy when required. In the case of flywheels used for torque smoothing, small amounts of energy are passively transferred in and out of the flywheel in synchronism with the pulsations of the internal combustion engine.

[0006] Thus, the energy stored per unit mass of rotor material in an energy storage flywheel is approximately 10 to 100 times greater than that of flywheels used for engine torque smoothing, and energy storage flywheels need to be volumetrically compact and lightweight to offer performance competitive with other energy storage technologies such as batteries.

[0007] A major design challenge for inertial elements used in energy storage class flywheels is how to withstand the high centrifugal stresses induced by high peripheral speeds, while at the same time maximizing safety during operation of the energy storage flywheel.

[0008] One approach is to make the risk of structural failure of the rotor negligible, i.e. the flywheel inertial elements should not be subject to material damage. This can be done by using ultra-high quality materials, using non-destructive testing means to ensure material quality, and by carefully monitoring the use of the rotor, particularly the number of runs it undergoes. Such techniques have been developed by the aerospace industry, but the materials required and the monitoring performed are time consuming as well as costly.

[0009] Another approach is to accept that the inertial element may fail during operation, which is rare, but the debris released from the inertial element (which has high linear kinetic energy) must be contained using a casing so as not to cause damage to property or, in more serious cases, human casualties. This can be achieved at a relatively low cost compared to the first approach above, since lower-cost materials can be used for mass production and maintenance costs are lower, since less strict monitoring is required. However, to ensure safety, the mass of the containment element must be sufficiently larger than the mass of the contained inertial element, with experts recommending a calculation of approximately 10 times the mass of the inertial element. The size and expense required to implement such safety measures means that in the main practical implementation, energy storage flywheels (usually with monolithic steel inertial elements) are placed in underground containments. However, the installation costs are still high and there is less flexibility on how the stored energy can be installed.

[0010] A third approach is to make the inertial elements from fiber composites, which can result in a material that is substantially stronger than those in the above mentioned approaches. It was previously thought that composites would always fail in a relatively good manner, assuming that the inertial elements would theoretically break into many small particles that could be easily contained using a lighter and cheaper casing than in the second approach. However, some failure modes of the inertial elements can still be quite violent due to the high energy storage levels, which can generate high pressure inside the casing. Therefore, even flywheel energy storage systems that use composites for the inertial elements are usually placed in very thick and heavy containment vessels or underground storage vaults for safety reasons.

[0011] A fourth approach is to use a metallic material for the inertial element. The metallic material is usually steel, but instead of using a monolithic cylindrical design, this inertial element can be assembled from a stack of thin disks or laminae (thin plates). Since the highest stresses in a rotating disk are tangential and radial, using a set of thin disks means that the rotor can operate at peripheral speeds as high as a monolithic cylinder (or even higher). Indeed, using this approach, the stresses are actually lower, since the axial stresses are reduced. In case of a structural failure in the inertial element of the structure, only a small part of the entire inertial element will be ejected. This approach therefore allows a significant reduction in the level of containment required for safe operation of the flywheel, and allows the use of a much lighter casing. That is, no thick and heavy casing or installation of containment is required, significantly reducing costs, facilitating ground installation of the flywheel, and a compact configuration.

[0012] An important consideration with this fourth approach is to ensure that failure of one disk does not propagate to adjacent (and beyond) disks, otherwise cascading failures may occur, releasing fragments from two or more disks. Also, the disks / laminas need to be rigidly fixed together in a stack, and the stack must be connected to the shaft so that the rotor can sit in the bearings.

[0013] From a commercial perspective, it must be noted that the ability to manufacture flywheel rotors at low cost is important, as it remains cheaper to use alternative energy storage means such as electrochemical batteries or ultracapacitors, even though these other means offer an impractical solution for energy storage applications where the ideal energy storage solution would otherwise be a flywheel-based system.

[0014] US Patent No. 5,399,633 (Gabrys) discusses thin-walled flywheels and recognizes that the central hole in the disk results in high stresses, reduced peripheral speeds, and reduced performance, and that thin steel sheets may offer favorable high strength properties compared to thick monolithic cylinders.

[0015] Gabrys discusses two methods of connecting the disks and connecting means to the shaft for the bearing, one of which is described with reference to FIG. 12 of the '691 patent and is roughly reproduced in FIG. 1 (prior art) of the present application. This first method relies on joining the surfaces of the disks (1) using adhesive, soldering or brazing (2). The connecting means and shaft (3) are also joined.

[0016] The problem with this approach is that the joints are placed under very high stresses, requiring very strong joint materials to prevent failure at the joint. However, if the joint is strong, a crack that initiates in one lamina can propagate to another lamina, resulting in an undesirable cascade type failure. As a result, the favorable case of only one lamina failure is not realized.

[0017] The reason for the high stresses at the interface is explained below with reference to Figure 1 (prior art) of the present application, which for ease of explanation is annotated with reference to Figure 12 of Gabrys.

[0018] When the disks rotate at high speeds, the maximum radial and tangential stresses occur in the region around the center of the disk. This reduces the axial thickness of the disk due to the Poisson's ratio effect by an amount shown as Δt. The cross-sectional shape of each disk during rotation is shown in dotted lines, although the deformation has been exaggerated for illustrative purposes. Because the bond is relatively thin, it is difficult for the disks to absorb the effects of pulling apart at the bore unless the bond is very strong.

[0019] Also, if the diameter of each minor disc is smaller than that of the main disc, there is another problem with the shaft connection means: the radial stretch of the upper minor disc, denoted Δr2, will be less than the stretch of its adjacent main disc, Δr1. This will cause significant shear stresses in the joint, which must be strong enough to resist them.

[0020] However, a strong seam bond does not prevent cascading failures in the event of a crack in one of the disks, for the reasons mentioned above. In this case, the crack will most likely form around the center of one disk. As the crack grows radially outward across the disk, the stress in the two adjacent disks will increase due to the load being transferred to these disks through the strong bond. Given that these adjacent disks are already operating under high stress, this increase in local stress may well cause the adjacent disks to crack. This sequence is repeated until some, if not all, disks crack, resulting in a highly undesirable multiple disk failure mode.

[0021] Finally, adding a step (see figure 13 in Gabrys) may strengthen the joint, but it places high stresses on the disk at the corners of the step on the female side of the mating. Steps are also expensive to manufacture.

[0022] Sanders et al. attempts to solve some of the above problems by using spigots on each of the disks and collars between each of the joints. However, these joints require precision manufacturing. While this is feasible for limited production of the very heavy flywheels described by Sanders, it would be prohibitively costly for mass production of flywheels. Also, this structure is somewhat unstable in use, assuming the joints have small diameters and the disks are not mechanically locked together.

[0023] US Patent No. 5,399,633 (Pullen) discloses a laminated flywheel structure in which bolts are inserted through specially shaped holes through the disks to reduce stress in the holes. Figure 2 (prior art) of the present application shows Figure 14 of US Patent No. 5,399,633, in which a disk stack (12) is clamped between two end plates (20) using an array of bolts (42, 44). The end plates (20) allow the disk stack to be connected to a shaft for rotation. The bolts pass through specially shaped holes in the disks (12) and are fixed in place in the holes by inserts. The disks with holes in US Patent No. 5,399,633 are intended to operate at the same speed as disks without holes. However, to ensure the stability of the flywheel, the structure requires precision fits between its parts, which is expensive. [Prior art documents] [Patent documents]

[0024] [Patent Document 1] U.S. Patent No. 7,267,028 [Patent Document 2] U.S. Patent No. 10,138,980 [Patent Document 3] European Patent No. 2759043 Summary of the Invention

[0025] It is an object of the present invention to reduce or substantially avoid the above problems and provide a flywheel which can be manufactured at relatively low cost whilst ideally providing safety features which match or exceed those provided by laminated construction.

[0026] According to a first aspect of the present invention, there is provided a flywheel comprising: a plurality of disks (laminas) arranged in a stack, including at least first and second end disks at opposite ends of the stack, each of the plurality of disks including a plurality of disk holes extending therethrough; first and second plate members (cheek plates) disposed at opposite ends of the stack, one or both of the first and second plate members including a plurality of plate holes therethrough that align with a corresponding set of disk holes in the stack; and connecting means for clamping the first and second plate members together with the stack of disks, the connecting means extending through each of the plurality of disk holes without contacting the plurality of disks.

[0027] The flywheel is safer than conventional flywheels because the connection means (e.g., one or more bolts) do not contact the disk holes, but only the plate members. This helps to avoid excessive stresses being transferred from the connection means to the disks during rotation of the flywheel that would otherwise contribute to crack formation / propagation and catastrophic failure. The flywheel can be operated safer and for longer periods of time at the high rotational speeds required for significant energy storage (preferably supersonic, as opposed to the speed of sound in air at atmospheric pressure).

[0028] The flywheel has a kinetic energy storage capacity of at least 100 kilojoules (kJ) during use. Preferably, the flywheel has a kinetic energy storage capacity of at least 200 kJ, or at least 250 kJ, or at least 300 kJ.

[0029] This flywheel has a rotational speed of at least 350 meters per second (ms -1 ) peripheral speeds can be achieved.

[0030] The flywheel (specifically its inertia element) has a minimum stored energy, during use, of 25 kJ / kilogram.

[0031] Each disk is considered an inertial element (stacked element) of the flywheel. The disks are arranged or structured into a stack that stores most of the kinetic energy in the flywheel during rotation.

[0032] The disk holes may be offset from the long axis (axis of rotation) of the stack, which is the axis about which the stack rotates when in use as part of a flywheel.

[0033] The minimum width (diameter) of each plate hole is substantially smaller than the width of each disk hole, in other words the disk holes in a linear series are wider than the plate holes bordering the ends / both ends of the series of disk holes.

[0034] This means that the, or each, plate hole may provide support for the connection means and it also provides a space (gap) around the connection means separating it from the wall of the disk hole, which may be an air-filled space.

[0035] The connecting means is not supported by the disc hole, i.e. the entire length of the connecting means located within the disc hole is spaced from the disc hole without any bridging or supporting structure extending across the space from the disc hole wall to the connecting means.

[0036] Each disk hole has a sidewall facing the connecting means, each sidewall extending in a direction along the stack from one side of the disk to the other, and together providing at least one substantially uninterrupted (continuous) bore through the stack.

[0037] The first and / or second plate members include one or more clamping regions that abut the first and / or second end disks, respectively. The first and / or second plate members include at least one recessed region that is substantially spaced from the end disks, respectively.

[0038] In this manner, the or each plate member is shaped to clamp at a peripheral (outer) region of the disk stack, for example to clamp an annular region of an end disk. One or more recessed regions space a second region of the or each plate member from the one or more end disks. This helps to minimize stresses resulting from, for example, differential radial movements of the disks and plate members, optimizing safety during flywheel rotation and flywheel performance.

[0039] The or each plate member should ideally be structured so that it is subjected to the same or similar stress levels as those experienced by the disk during use.

[0040] The mass of the one or more plate members should be selected such that the containment requirements for installations around the flywheel to safely contain outgoing plate debris in the event of catastrophic failure of one or more plate members do not significantly exceed the containment requirements for a scenario in which a portion of the disk stack fails catastrophically.

[0041] The one or more recessed areas may be closer to the centre of the stack than the one or more clamping areas, and the or each plate member has one or more additional areas which engage (abut) the one or more end disks inwardly from the recessed area, at a central area of ​​the one or more end disks.

[0042] At least one recessed area is substantially a depression. At least one recessed area is substantially annular in shape, i.e., the shape of the adjacent recessed area or areas causes the empty following surface of the or each end disk to be substantially annular.

[0043] The recessed area provides space between a portion of the plate member and the opposing end disk surface, and its annular shape helps to evenly distribute forces during flywheel rotation.

[0044] In order to minimize slippage between adjacent disks during use, one or more layers of material (films) are provided between at least one pair (preferably each pair) of adjacent disks in the stack, the one or more layers (films) being provided on a surface of one of the adjacent disks of the pair, the layer of material being different from the main material of the disks.

[0045] During use, despite being connected (clamped) by the plate members, over time the disks may begin to slip relative to one another, which is undesirable. Providing the disks with one or more layers minimizes or substantially prevents the disks from slipping relative to one another during use. This also minimizes or substantially prevents the end disks from slipping relative to the plate members during use. In other words, slip is inhibited at disk-disk and disk-plate joints. Of course, the joint that prevents slip must not be too strong, otherwise a crack from one disk may cross or propagate to an adjacent disk.

[0046] Such one or more layers of material may include any one or more of thermoplastics, thermoset plastics, and soft metals or alloys, such as low melting point metals / alloys. Examples of low melting point alloys are solders or brazes.

[0047] The material of the layer or layers is selected to have a melting point below about 600° C. This is particularly beneficial if the disk is made of steel, as temperatures above 600° C. can adversely affect the structure / strength of the steel, i.e. its heat treatment.

[0048] The one or more layers (membranes) include a substantially annular layer (membrane) for at least one pair (preferably each pair) of adjacent disks, the annular layer (membrane) being disposed so as to partially or entirely surround each disk aperture.

[0049] During flywheel rotation, the discs may thin and separate from one another to some extent, which, as previously described, minimizes the contact area between the opposing central regions of adjacent discs. By applying the layer as an annular layer, this in-use disc separation does not significantly affect the interfaces between adjacent discs or the interfaces between one or more end discs and the adjacent plate members.

[0050] In some cases the layer may be applied only around the disc holes where maximum clamping pressure is applied, which is sufficient to prevent slippage while minimizing the overall contact area between adjacent discs during use.

[0051] The one or more layers are applied to each disk by plating or painting, or by applying a thin film to each disk when the disk stack is assembled prior to connecting the plate members to the stack.

[0052] A multi-layer (membrane) may be provided on at least one pair (preferably each pair) of adjacent disks, each of which is arranged to partially or completely surround a disk hole. The multi-layer (membrane) on the surface of the or each disk may include a plurality of partial monolayers (membranes), each of which is arranged in a common plane between the pair of disks.

[0053] It is also understood that some adjacent pairs of disks in a stack may have an annular layer (membrane) between them, while some adjacent pairs of disks in a stack may have multiple layers (membranes) between them.

[0054] The connection means includes one or more bolts, rivets, or threaded studs. The one or more bolts or rivets or threaded studs include a side wall having an outer surface that fits within a series of aligned disk hole walls.

[0055] The multiple connection means are arranged on a pitch circle which minimizes stress transfer between the disks.

[0056] Each bolt or threaded stud, respectively, is selected to be either solid or hollow.

[0057] The use of hollow bolts / studs minimizes weight and reduces stress on the bolts / studs, which also minimizes stress on the plate members.

[0058] The cross-section of each bolt or stud may be substantially constant.

[0059] The outer surface of some or all of one or more bolts or studs may taper (narrow) inwardly toward a central region of the bolt or stud, i.e., some or all of the bolts or studs may have a tapered outer surface cross-section (longitudinal cross-section).

[0060] The outer surface of some or all of one or more bolts or studs may include multiple (two, or three, or more than three) inwardly tapered sections. For example, there may be two tapered sections along the bolt / stud. That is, the bolt / stud may have an untapered thickness in its central and end sections, and a tapered (thinner) section between the central section and each end section.

[0061] Where two or more tapered sections are provided, they are spaced apart along the bolts / studs and / or separated by non-tapered sections for support by an appropriate number of intermediate support members, each tapered section being thinnest at a location substantially equidistant between two adjacent intermediate support members or between an intermediate support member and each of the end plates, depending on the number of intermediate support members and tapered sections.

[0062] Where multiple tapered sections are provided, the outer surface of the bolt / stud can be thought of as undulating in thickness increasing and decreasing along the bolt / stud.

[0063] The use of tapered bolts / studs minimises weight (especially if hollow) and reduces stress in the bolts / studs, which in turn minimises stress on the plate members.

[0064] The exterior cross-section of some or all of the one or more bolts or threaded studs may be curved to minimize stress in the one or more bolts or studs, i.e., some or all of the one or more bolts or studs may have a curved exterior cross-section (longitudinal cross-section).

[0065] The exterior surface of some or all of one or more bolts or studs may include multiple (2, or 3, or 4 or more) curved portions along each bolt / stud. For example, there may be two curved sections along a given bolt / stud, where the bolt / stud has, for example, a straight section in its center (or the cylindrical portion of the bolt / stud), optionally has similar sections at its ends, and has curved sections between the center and each end.

[0066] Where two or more curved sections are provided, they may be equidistantly spaced along the bolt / stud and / or separated by straight or linear sections for support by an appropriate number of intermediate support members, each curved section being thinnest at a location substantially equidistant between two intermediate support members or between an intermediate support member and each of the end plates, depending on the number of intermediate support members and curved sections.

[0067] The exterior surface of some or all of one or more bolts or threaded studs may be elliptical in cross section.

[0068] Using bolts / studs with a curved outer cross section (longitudinal cross section) minimizes weight (especially if hollow) and reduces stress in the bolts / studs, which can also potentially minimize stress on the plate members more than tapered bolts / studs.

[0069] One or more of the bolts or threaded studs may be curved, i.e., the bolt or stud extends along (or follows) a curved longitudinal axis, for example approximating or following at least a portion of a catenary curve.

[0070] The catenary shape reduces stresses in the bolt / stud and may also reduce stresses in one or more plate members. It will be appreciated that if the catenary shaped bolt / stud does not contact the plate member perpendicularly (orthogonally), the plate member may include a corresponding angled (sloped) surface to position the bolt / stud and minimize stresses in the connection during use.

[0071] Each disk hole in the series of disk holes is substantially the same shape and size.

[0072] The plate holes may have a different shape than the disk holes.

[0073] The size of the disk and / or plate holes needs to be relatively larger for catenary bolts / studs than for straight bolts / studs so that when a curved bolt / stud is placed through a series of disk holes it does not contact any of the adjacent disks.

[0074] A first set of disc holes in a given series are aligned along a first common linear axis. A second set of the disc holes are aligned along a second common linear axis. The second common linear axis is offset from and substantially parallel to the first common linear axis. One or more additional sets of disc holes may be aligned along respective one or more additional common linear axes. These features may be provided when the connecting means is curved.

[0075] In other words, instead of an array of substantially identical disk holes aligned on one common axis, two or more different shapes and / or positions of disk holes in a series may be provided, particularly for receiving catenary bolts / studs, i.e. two or more disk types may be provided, allowing some or all of the disk holes to be relatively small whilst maintaining the structural integrity of each disk.

[0076] The plurality of discs includes one or more intermediate discs, or preferably two or more intermediate discs, disposed between the first end disc and the second end disc.

[0077] At least one intermediate support member (or plate) is disposed between the end disks adjacent one or more intermediate disks. At least one intermediate support member may be disposed between two intermediate disks in the stack to support the connection means in the stack. The intermediate support member may be disposed in the center of the stack.

[0078] If the bolts or studs are relatively long, they may be subject to high stress during flywheel rotation. To compensate for this, one or more intermediate plates in the disk stack support the bolts or studs in one or more areas in the middle (or midway) of the stack. If the bolts / studs have multiple tapered or curved sections, multiple intermediate plates may be provided to support some or all of the non-tapered or non-curved sections of the bolts / studs.

[0079] The one or more intermediate plates may be of a different diameter than the discs and / or plate members. The diameter of the intermediate plates may be smaller than the diameter of the discs.

[0080] The one or more intermediate plates may be shaped differently than the disks and / or plate members. For example, the intermediate plates do not have to be shaped like disks with holes. The one or more intermediate plates may be formed in a similar shape to the plate members to reduce flywheel stresses during rotation.

[0081] Locating means are provided for locating the disk holes of the first and / or second end disks relative to the first and / or second plate members respectively.

[0082] The connection means are located only on one or more plate members (and optionally one or more intermediate plates) and, for safe operation of the flywheel, it is also necessary to securely locate each end of the stack on one or more plate members.

[0083] The positioning means may include one or more spacers, such as one or more washers.

[0084] The or each spacer includes a spacer body having a first sidewall and optionally a second sidewall, the first sidewall configured to fit at or within one of the disk holes, and the second sidewall configured to fit at or within a corresponding recess in one of the plate members.

[0085] The or each spacer may have a contour similar to the contour of the end disk hole.

[0086] When multiple spacers are provided, some or all of the spacers may be formed to precisely fit the plate member (or portion thereof) and / or to precisely fit the end disk.

[0087] The or each spacer fits within a corresponding pocket or recess in the plate member and is preferably located relative to each of the or each of the plate holes. The pockets / recesses are circular and / or countersunk.

[0088] The first sidewall is formed with a shape that is complementary to or corresponds to the shape of the end disk hole. The first sidewall may have an elliptical or approximately elliptical profile. The first sidewall may have a circular or approximately circular profile.

[0089] The second side wall is formed with a shape that is complementary or corresponds to the shape of the pocket / recess in the plate member. The second side wall may be elliptical or approximately elliptical in profile. The second side wall may be circular or approximately circular in profile.

[0090] The first sidewall can be approximately the same height as the second sidewall.

[0091] The spacers have a width / diameter (along the x-axis and / or y-axis) greater than their depth / thickness (along the z-axis). The spacers may be of a depth substantially less than the depth of the end disks and / or the depth of the plate members.

[0092] A generally elliptical disk hole can minimize disk hole stresses during flywheel rotation. Having corresponding elliptical spacer side walls provides a good fit to reduce stress transfer to each disk hole that the spacer contacts in the stack.

[0093] The first side wall may be wider than the corresponding disk hole so as to fit within the disk hole when the plate member is clamped against the stack.

[0094] The second side wall may be wider than the corresponding disk hole to fit within the disk hole when the plate member is clamped against the stack.

[0095] In other words, to avoid the need for precision-fitting spacers and thus reduce costs, the or each spacer may be oversized compared to either or both of the disk hole and / or the recess in the plate member, and when the spacer is in place to connect / clamp the plate member to the stack, it will fit into the available space after the plate member is fixed to the stack (an interference fit).

[0096] In some cases, it may be preferable to produce precision machined spacers, for example to provide a precision fit for the plate member holes. Other parts, such as the parts to fit into the disk holes, may be oversized as described above. This may provide some cost savings, especially when the disk holes are non-circular and the plate member holes are (approximately) circular.

[0097] The first and / or second plate members may each include a peripheral lip configured to mate with a periphery of one or both of the first and second end disks.

[0098] The first and / or second plate members each include a plurality of spaced apart lip members configured to engage against a plurality of regions of the periphery of one or both of the first and second end disks.

[0099] The lip or lip member can be thought of as a continuous or partial version of the same means for engaging the periphery of the disks. The lip or lip member can be used in place of or in conjunction with the positioning means (such as spacers) discussed above for positioning the plate member relative to the disk stack.

[0100] One or more of the end discs may be a precision manufactured diameter, with the lip or lip member being precision manufactured to fit that diameter.

[0101] According to a second aspect of the present invention there is provided a flywheel comprising: a plurality of disks (lamina / laminas) arranged in a stack, including at least first and second end disks at opposite ends of the stack, each disk including a central region and a peripheral region surrounding the central region, the peripheral region being adjacent (or near) a periphery of the disk; first and second plate members (or cheek plates) disposed at opposite ends of the stack; and joining means for joining only a portion of each disk in the stack to each adjacent disk, including joining adjacent peripheral regions of adjacent disks to one another; and joining means for joining each of the first and second plate members to the first and second end disks of the stack, respectively.

[0102] This flywheel is safer than conventional flywheels because the joining means only joins a portion of each disk face to the adjacent disk or plate member. The structure relies solely on the joining of the disks to the disk and plate members to maintain structural integrity. The center regions of the disks are not joined to one another.

[0103] Unlike strong seam bonds across the entire surface of each disk, such partial bonds avoid cascading failures if one of the disks cracks. Bonding in the peripheral regions helps minimize the chance of a crack propagating from the center of the disk during flywheel rotation that could otherwise lead to catastrophic failure. The flywheel can be operated safer and for longer periods of time at the high rotational speeds (preferably supersonic, as opposed to the speed of sound in atmospheric air) required for significant energy storage.

[0104] In this aspect of the invention, the flywheel does not include clamping means for clamping the disks together in the stack, i.e. there are no clamping elements which clamp the plate members to the stack.

[0105] The flywheel disc does not need to include disc holes for the connecting elements, and the plate members do not need to include one or more plate holes for the connecting elements.

[0106] The joining means may include an adhesive, for example an epoxy resin. Any suitable strong adhesive or engineering glue that will withstand the rotation of the flywheel may be used.

[0107] The strength of the joining means / material (both to each disc surface and within the body of the joining means) should be selected so that the flywheel maintains sufficient structural integrity while rotating, but in the event of a crack in the disc, resists / mitigates crack propagation through the joint area.

[0108] The adjacent central regions of adjacent pairs of disks may be spaced apart, including the spaced apart central regions when the flywheel is stationary (i.e., not rotating), to account for the thinning of the disks that occurs during flywheel rotation, as previously described.

[0109] The peripheral region of at least one (preferably some or all) of the disks is at least slightly thicker than the central region of that disk in order to space the central regions, i.e., the adjacent central regions of an adjacent pair of the disks, apart. It is understood that this limits the contact area between adjacent disks. The contact area may be less than 100% of the disk-facing area of ​​a given disk.

[0110] According to this, a disc may be provided with a raised area or seat on one or both sides which joins to another raised area or seat of another disc / plate member.

[0111] The provision of the seats limits the size of the bond area between adjacent discs to a relatively small area or annulus, which means that Poisson's thinning peeling effect is reduced or does not occur during flywheel rotation.

[0112] The seating can be formed, for example, by stamping the disk, although other suitable means can be used. Stamping can form a relatively uniform seating and can also reduce the thickness of the disk in a central region (on one or both end faces of the disk). It will be appreciated that the stamping process need only result in a change in disk thickness on the order of microns, as long as the seating is sufficiently elevated from the thinner central region of the disk to reduce / avoid the delamination effect discussed above.

[0113] The peripheral region of at least one disc (and preferably some or each of the discs) includes a substantially flat surface or seating which is joined to a corresponding substantially flat surface or seating in the peripheral region of an adjacent disc.

[0114] One or more shims (or seating elements) may be provided for one or more of the adjacent pairs of disks in the stack to space the central regions apart. The or each shim (or seating element) is bonded to adjacent peripheral regions of the adjacent pair of disks, optionally on both sides. The adjacent central regions of the adjacent pair of disks are spaced apart by the one or more shims.

[0115] The shim or seating element may be thin compared to the thickness of a given disk.

[0116] The shims may be made of a metal, metal alloy, or other suitable material. If the shims are made of a metal or metal alloy, they may include or be either steel, aluminum, or titanium, although other suitable metals / alloys are contemplated and this list should not be construed as exhaustive.

[0117] The joining means may comprise or consist of one or more annular joining areas between each pair of adjacent disks in the stack. If any shims are provided, the one or more shims may be substantially annular in shape.

[0118] During flywheel rotation, the discs may thin to some extent and separate from one another, and providing a peripheral annular joint between the discs, possibly via a shim member, means that the thinning of the discs reduces the impact on the joints between adjacent discs and / or between one or more end discs and an adjacent plate member.

[0119] According to a third aspect of the present invention there is provided a flywheel comprising: a plurality of disks arranged in a stack, including at least first and second end disks at opposite ends of the stack, each of the plurality of disks including a plurality of disk holes extending therethrough; first and second plate members disposed at opposite ends of the stack, one or both of the first and second plate members including a plurality of plate holes extending therethrough which align with a corresponding series of disk holes extending through the stack, one or both of the first and second plate members including one or more recesses on a disk-facing side of the plate member and disposed adjacent one or more of the plurality of plate holes; and first and second plate members, connecting means for clamping the first and second plate members together to the stack of disks, the connecting means extending through each of a plurality of disk holes, with spacers or space-filling means provided between the or each connecting means and each disk hole to support the connecting means, the spacers or space-filling means extending from a position in the stack into one or more recesses in one or both of the first and second plate members.

[0120] The flywheel is safer than conventional flywheels because the connection means (e.g. one or more bolts) are supported within the stack along some or all of its length. This reduces or more evenly distributes stress transfer from the connection means to the disk holes, thereby minimizing the possibility of cracks forming in the disks or propagating between disks during rotation of the flywheel, which could otherwise lead to catastrophic failure. The flywheel can be operated safer and for longer periods of time at the high rotational speeds required for energy storage (preferably supersonic, as opposed to the speed of sound in air at atmospheric pressure).

[0121] The spacer or space filling means may be in the form of a sleeve which extends into one or more recesses in one or both of the plate members, the sleeve being elongated.

[0122] A sleeve is fitted around the connecting means, the sleeve having an outer wall contour that substantially matches or corresponds to the inner wall contours of some or all of the disk holes in the series of aligned disk holes in the stack, providing a snug fit within the disk holes.

[0123] The sleeve may be rigid or flexible. The sleeve preferably contains one or more cavities or channels when the sleeve is flexible. The cavities / channels may be considered as cut-outs or portions of the molded contour of the sleeve, although it will be appreciated that molding is not the only means of forming the sleeve.

[0124] The channels help reduce the mass of the spacer (compared to a solid equivalent), minimize stress between the sleeve and the one or more disk holes with which it contacts, and may also increase the flexibility of the spacer to more evenly spread the load across the one or more disk holes.

[0125] The spacers or space filling means may be comprised of a hardenable material, i.e. a material that hardens, dries, hardens or hardens after being applied to the flywheel.

[0126] This material can be injected or otherwise introduced into the flywheel after the other portions of the flywheel have been assembled, thereby simplifying the mechanical assembly process.

[0127] The connecting means may include a conduit for the passage of a flow of material suitable for forming a hardenable material, the conduit providing a flow path to or into one or more of the disc recesses and the space between the connecting means and the disc aperture. The conduit may be provided within or through the connecting means.

[0128] The curable material may include any one or more of a thermoplastic material, optionally with or without reinforcing fillers or fibers, a thermoset plastic material or an epoxy, optionally with or without reinforcing fillers or fibers, and a soft metal or a low melting point metal (or metal alloy).

[0129] A flywheel according to any one of the above-described aspects of the invention may include any feature or combination of individually selected features presented in relation to the other aspects of the invention, to the extent that the inclusion of the selected feature is not inconsistent with a feature of that aspect of the invention.

[0130] A flywheel assembly is provided that includes one or more flywheels according to one or more of the above-described aspects of the invention.

[0131] The or each flywheel is attached to or with a drive assembly for facilitating rotation of the or each flywheel to store or extract energy from at least one flywheel. The drive assembly may be mechanical, electrical or any other suitable form of drive means. [Brief description of the drawings]

[0132] For a better understanding of the invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Figure 1] FIG. 1 shows a side view of a first prior art flywheel device based on Patent Document 1. [Diagram 2] FIG. 2 shows a side cross-sectional view of a second prior art flywheel device based on US Pat. No. 5,399,633. [Diagram 3] FIG. 3 shows a side cross-sectional view of a first embodiment of a flywheel, in which FIG. 3A shows a top view of a disk of said flywheel. [Figure 4] 4A shows a side sectional view of a second form of the flywheel connection means of FIG. 3, FIG. 4B shows a side sectional view of a third form of the flywheel connection means of FIG. 3, and FIG. 4C shows a side sectional view of a fourth form of the flywheel connection means of FIG. 3. [Diagram 5] FIG. 13 shows a partial cross-sectional side view of a second embodiment of a flywheel including a fifth form of connecting means. [Figure 6] FIG. 13 shows a partial cross-sectional side view of a third embodiment of a flywheel including a fifth form of connecting means. [Figure 7] FIG. 13 shows a partial cross-sectional side view of a fourth embodiment of a flywheel including an intermediate support member. [Figure 8] FIG. 8 shows a top view of a disk of any of the flywheels of FIGS. 3, 5, 6 and 7 including a first embodiment of a surface layer applied to the disk. [Figure 9] FIG. 8 shows a top view of a disk of any of the flywheels of FIGS. 3, 5, 6 and 7 including a second embodiment of a surface layer applied to the disk. [Figure 10] 10A shows a partial cross-sectional side view of a fifth embodiment of a flywheel, in which FIG. 10A shows a perspective view of a first form of positioning means of said flywheel; FIG. [Figure 11]11A shows a partial cross-sectional side view of a sixth embodiment of a flywheel, in which FIG. 11A shows a perspective view of a second form of positioning means of said flywheel. [Figure 12] FIG. 12A shows a partial cross-sectional side view of a seventh embodiment of a flywheel, in which FIG. 12A shows a perspective view of a third form of positioning means of said flywheel. [Figure 13] 13A shows a partial cross-sectional side view of an eighth embodiment of a flywheel, in which FIG. 13A shows a perspective view of the flywheel. [Figure 14] 14A shows a partial cross-sectional side view of a ninth embodiment of a flywheel, in which FIG. 14A shows a perspective view of the flywheel. [Figure 15] In the figures, FIG. 15A shows a side cross-sectional view of a tenth embodiment of the flywheel, FIG. 15B shows a partially enlarged side cross-sectional view of the flywheel of FIG. 15A, and FIG. 15C shows a partially enlarged side cross-sectional view of a modified example of the flywheel of FIG. 15A. [Figure 16] 16A shows a side cross-sectional view of an eleventh embodiment of a flywheel, in which FIG. 16A shows a perspective view of a first embodiment of a spacer to a connection means of the flywheel, and FIG. 16B shows an end view of a second embodiment of a spacer to a connection means of the flywheel. [Figure 17] 17A and 17B show side cross-sectional views of a twelfth embodiment of a flywheel, in which FIG. 17A shows a partially enlarged side cross-sectional view of the flywheel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0133] 1 and 2 relate to a prior art device described in the Background section.

[0134] Figures 3 and 3A relate to a first embodiment of a flywheel generally designated "100." Flywheel 100 is designed for use in kinetic energy storage that can be used in conjunction with a suitable electric motor-generator or mechanical drive (or other suitable type of drive means) to provide a means of storing electrical energy.

[0135] The flywheel 100 has many possible applications including, but not limited to, one or more of local grid boosting for fast charging electric vehicles, uninterruptible power supplies, trackside rail, demand side management, and electric grid services, as some examples. The flywheel 100 can be installed in any vehicle with an electric propulsion system, such as a car, truck, bus, train, plane, or ship.

[0136] Flywheel 100 may also be used to provide kinetic energy storage, capable of mechanically transferring stored energy to assist an accelerating vehicle and recover otherwise lost kinetic energy. The structure of flywheel 100 will be described primarily with respect to a stationary flywheel, unless otherwise noted.

[0137] The flywheel 100 includes a plurality of discs 102 (also referred to as lamina). In this embodiment, fourteen discs 102 are provided, however, it will be appreciated that in other embodiments any suitable number of discs may be provided, provided that at least first and second end discs are present.

[0138] The disks 102 are substantially circular in outline in this embodiment. The centres of the disks 102 are aligned along a common longitudinal axis (axis of rotation) AA to provide a stack of disks 104. The stack 104 is substantially cylindrical in this embodiment.

[0139] The stack 104 is assumed to provide the inertial element for the flywheel 100. The stack 104 can be considered as a stack of laminations.

[0140] The disks 102 are each made from steel in this embodiment, although other suitable metals, alloys, or composite materials may be used in other embodiments.

[0141] Each disk 102, in this embodiment, has a number of disk holes 102a. Each disk 102 in the stack is substantially identical, in this embodiment, preferably with a tolerance on the order of a few microns or tens of microns.

[0142] One of the disks 102 is shown in Figure 3A and has four disk holes 102a. The disk holes 102a of each disk 102, in this example, are aligned on a common axis with corresponding disk holes in other disks in the stack 104. This provides multiple sets or series of aligned disk holes (four sets in this example) through the stack, which may be considered as stack holes.

[0143] It will be appreciated that any suitable number of disk holes, in any suitable location and size, may be provided through the disk 102 such that the disks are secured together by a connecting means.

[0144] The disk holes 102a are located near the periphery of each disk 102. The disk holes 102a are equally spaced about axis AA. The disk holes 102a are assumed to be located on a pitch circle indicated by the imaginary circular dashed-dotted line in Figure 3A. In this example, the disks each have four-fold rotational symmetry when viewed from an end face.

[0145] The shape of the disk hole 102 is selected to minimize stresses as the disk rotates at flywheel speed, details of suitable shapes are given in US Pat. No. 5,393,633, which is incorporated herein by reference.

[0146] Each disk hole 102a is generally elliptical in outline in this embodiment, with the pitch circle intersecting the center of each disk hole in Figure 3A, although it will be appreciated that other embodiments include disk holes of various other non-circular shapes, or in some cases circular disk holes.

[0147] A pair of plate members 106 (also referred to as cheek plates) are disposed on either end of the stack 104. The plate members 106 are fixed or clamped together relative to the stack 104. The plate members 106 in this embodiment each have a diameter smaller than the diameter of the disk stack 104.

[0148] The cheek plates 106 allow the lamination stack 104 to be connected to a bearing seat 150. The cheek plates 106 also allow the stack 104 to be connected or mated together (or more broadly provided in operative engagement with) an electric machine rotor portion or a mechanical drive portion 160.

[0149] Each plate member 106 has a stack-facing central portion 108 that contacts a corresponding central region of one of the end disks 102 .

[0150] Each plate member 106 has a substantially annular stack-facing portion 110 disposed about a central portion 108. The annular portions 110 are slightly recessed away from each of the end disks 102 of the stack 104. The annular portions 110 have a concave contour.

[0151] Each plate member 106 has a second substantially annular stack-facing portion 112 disposed about the first annular portion 110. The second annular portion 112 provides a clamping area for securing the plate members 106 together to the stack 104.

[0152] A plate hole 106a is provided through each plate member for receiving a connecting means. The plate holes 106a are narrower than the disk holes 102 where they open into the stack 104. The plate holes 106a have a diameter which corresponds substantially to the outer diameter of the connecting means in this embodiment.

[0153] Each plate member 106 is thickest at the longitudinal axis AA in this embodiment. Each plate member 106 gradually thins radially outward from the axis AA. The thinnest portion of each plate member 106 is approximately in the center of the first annular portion 110. Each plate member 106 has an outer recessed region opposite the stack-facing recess 110. Moving further radially outward, each plate member 106 becomes somewhat thicker at the second annular portion 112 than the recessed region.

[0154] Of course, the above-described form of the plate member should not be considered essential to the invention: a plate member similar to the prior art as shown in Figure 2 may instead be used in the relevant embodiment.

[0155] Although the flywheel has been described above as having two plate members, it will be appreciated that embodiments are envisaged in which only one plate member is provided at one stack end, with the other stack end having a plate member fixed in place to clamp the stack of disks together.

[0156] Connection means are provided for securing the plate members together, in this embodiment a plurality of connection means being provided, the connection means in this embodiment being clamping means in the form of a plurality of bolts, rivets or threaded studs, which may be broadly referred to as clamping elements 114.

[0157] Each of the four clamping elements 114 in this embodiment is positioned through the centre of a series of disc holes 102. The clamping elements 114 are provided on a pitch circle. The ends of the clamping elements 114 are secured by fastening means 116 (e.g. nuts or the like) which abut against the plate members 106 and provide a clamping force against the stack 104.

[0158] The plate member 106 is provided with a recessed or countersunk exterior area 118 for receiving a fastening means. In this embodiment, the male threads on the end of each clamping element 114 are disposed in the countersunk area.

[0159] The clamping element 114 does not contact the disk 102 or the disk hole 102a. The clamping element 114 is supported only by the plate member 106 in this embodiment. This reduces stress in the thin layer 102 at the disk hole 102a during high speed flywheel rotation since the disk hole 102a does not provide support for the clamping element 114.

[0160] A gap is provided between the outside of each clamping element 114 and the surrounding inner peripheral wall of the disk hole 102a. The curved disk hole wall portions immediately adjacent each side of the clamping element 114 are most clearly seen in cross section in FIG.

[0161] The flywheel 100 may be provided as part of an assembly with a suitable drive mechanism, which may be considered to be part of an energy extraction and distribution system, within a containment suitable for safe operation of the flywheel, taking into account the mass and energy storage capacity of the flywheel.

[0162] In use, the flywheel 100 is rotated about axis AA by a drive mechanism to store kinetic energy in the flywheel 100. When used to store significant amounts of kinetic energy, the flywheel 100 can deform radially outwardly with speeds on the order of hundreds of meters per second.

[0163] The drive mechanism can be used to distribute some of the stored kinetic energy in the spinning flywheel by reducing the rotational speed of the flywheel, extracting the stored kinetic energy and converting it to another useful form, such as electrical energy. Further examples of energy collection and extraction are performed as needed, which can include thousands or millions of cycles of energy distribution on the order of hundreds of kilojoules, megajoules, or more, for example, when multiple flywheels are provided in an assembly and operated together in parallel.

[0164] Variations of the above flywheel embodiments and components are envisioned within the scope of the present invention. The features / functions of the following embodiments are similar to those described above unless otherwise stated.

[0165] Like reference numbers are used in the following embodiments to refer to like features / functions, with each number incremented by a multiple of 100, e.g., feature 102 corresponds to feature 202, 302, etc. in the subsequent embodiments.

[0166] 4 shows a first form of clamping element 114 for the flywheel 100. The clamping element 114 is solid and has a substantially constant cross-sectional width.

[0167] A second form of clamping element 114a (FIG. 4A) is envisioned in which the element is hollow rather than solid. A hollow bore extends through the entire length of element 114a as shown, although it will be understood that there may instead be several hollow areas or pockets provided within the element.

[0168] A third form of clamping element 114b (FIG. 4B) is also envisioned, which is hollow and has a tapered outer cross-section, with the outer walls of element 114b tapering inwardly from both ends toward the center of element 114b, as shown.

[0169] Still further envisioned is a fourth form of clamping element 114c (FIG. 4C) which is hollow and has a concave (recessed) outer cross-section, the curvature of the outer cross-section providing an elongated intermediate section which is substantially thinner over the majority of the length of the element 114c.

[0170] Each of the clamp elements 114 to 114c of the first to fourth forms is a straight clamp element.

[0171] Figure 5 illustrates a fifth configuration of clamping element 214 (Figures 5 and 6) for a second embodiment of a flywheel generally designated "200." Flywheel 200 is similar to first flywheel 100, except for the clamping elements and plate members.

[0172] Element 214 is a curved clamping element. It is noted that the size of the disk hole 202a needs to be correspondingly larger than for a straight element in order to provide clearance between the clamping element 214 and the disk hole 202a.

[0173] Element 214 is solid in this embodiment, but may be hollow in other embodiments. Clamping element 214 follows a curved longitudinal axis. The curvature of element 214 substantially approximates a catenary (or a portion of a catenary). Element 214 may be optionally pre-formed prior to insertion into the stack.

[0174] The curved clamping element 214 is positioned in profile such that the convex side of the element is radially outward relative to the flywheel axis AA (see FIG. 3 for the location of this axis on the flywheel 200) than the concave side of the element.

[0175] Due to the curvature of the clamping elements 214, the plate members in this embodiment include angled recesses 218a, 218b for the fastening means 216. The recesses are angled such that they lie on an axis that is not perpendicular (orthogonal) to the plane of each plate member 206. In this embodiment, the angle is approximately 15 degrees relative to an axis perpendicular to the plane of the plate members 206. This angle will vary depending on the stack height, the diameter of the clamping elements 114, and the opening size of the disk holes 202a, but is typically in the range of 10 degrees to 30 degrees.

[0176] The first recess 218a is angled oppositely from the second recess 218b. It will be appreciated that a corresponding angled recess is provided for each curved clamping element through the stack 204.

[0177] Figure 6 shows the same clamping elements as Figure 5, but provided with a third embodiment of a flywheel generally designated "300." Flywheel 300 is similar to second flywheel 200, except for the disc difference.

[0178] In this embodiment, the stack of disks includes at least two different configurations or variations of disks 302. The first two disks 302x and the last two disks 302x in the stack are of a first configuration and have a first set of disk holes 302b that are aligned together along a first axis. The disks 302y in the stack between the two pairs of end disks 302x are of a second configuration and have a second set of disk holes 302c that are aligned together along a second axis.

[0179] The second axis is located radially outward of the first axis relative to the flywheel axis AA. Thus, the disk holes 302b, 302c can be smaller in size than the disk hole 202a in the embodiment of Figure 5, while still maintaining a clearance between the element 214 and the disk holes 302b, 302c.

[0180] It will be appreciated that the size and location of the disk holes are provided in a configuration that matches the size and shape of the clamping element that will pass through the stack, i.e., it is envisioned that more than two disk configurations may be provided, and in some embodiments each disk will have a disk hole that is slightly offset from its nearest neighbor, generally providing stack holes that reasonably approximate the shape of the non-linear clamping element.

[0181] 7 relates to a fourth embodiment of a flywheel generally designated "400." Flywheel 400 is similar to first flywheel 100, except for the difference in stack configuration.

[0182] In some embodiments, the number of discs 402 provides a long enough stack that the corresponding connecting elements 414 are subject to excessive stress during flywheel rotation. To alleviate this, a middle plate 420 is provided midway through the stack 404 to support the connecting elements 414 within the body of the stack. In this embodiment, there are 18 discs 402, divided into first and second groups of nine discs on each side of the middle plate.

[0183] The middle plate has plate holes 420 a that substantially correspond to the size and shape of the connecting elements 414 to support the elements 414 .

[0184] It is understood that the middle plate 420 may be a different size and / or shape than the disks 402 and / or plate members 406. For example, in some embodiments, the middle plate includes recessed areas in the plate surface to minimize contact areas with and stress on adjacent disks 402. This recessed area of ​​the middle plate may be concave and / or annular, similar to the recessed areas of the end plates.

[0185] It will also be understood that the intermediate plate can be used with any of the forms of connecting elements described herein, provided the intermediate plate holes and connecting elements are appropriately configured.

[0186] Figures 8 and 9 relate to material being provided as one or more layers between a given pair of adjacent disks. For simplicity, the reference numbers used refer to the first embodiment of flywheel 100, however, the one or more layers of material may be provided between any or all of the adjacent pairs of disks in a stack in any embodiment of the invention.

[0187] In Figure 8, a partial surface layer 122 is provided on the peripheral annular surface area of ​​the disk 102 and passes around the holes 102a. In Figure 9, a plurality of partial surface layers 124 are provided, each layer 124 being disposed around one of the holes 102a in a generally elliptical or oblong shape (although in other embodiments layers having a circular perimeter or a perimeter of other shape may be provided).

[0188] The layer or layers serve to minimize or substantially prevent rotation of one disk relative to its adjacent disk by increasing friction and reducing the likelihood of slippage. This is in addition to the clamping force provided by plate member 106, which also reduces slippage.

[0189] The or each layer may be made from a thermoplastic or thermosetting plastic or a soft metal or alloy such as solder. The plastic / metal is applied as a thin layer or film to one or both sides of the disk, in the shaded areas shown in FIG. 8 or the shaded areas shown in FIG. 9.

[0190] 10 and 10A relate to a fifth embodiment of a flywheel generally designated "500". The main difference with the first flywheel 100 is that each plate hole 506a is provided with a pocket or recess. Each pocket is provided on the stack-facing side of the plate member 506.

[0191] A number of spacers 526 are provided which fit into some or all of the pockets at either end of the stack. The spacers 526 provide a means for locating the ends of the stack of disks 502 relative to the plate member 506 and prevent relative movement of the portions. A hole 528 is provided through the center of each spacer to receive a selected connecting element.

[0192] The size and shape of each spacer 526 is configured to fit snugly within a respective pocket and also within a respective end disk hole. Spacers 526 in Figure 10A have substantially oval sidewalls in this embodiment.

[0193] 11 and 11A relate to a sixth embodiment of a flywheel generally designated "600." This embodiment is similar to the fifth flywheel 500 and its hole spacers 526. However, each spacer 626 in this embodiment has an oval sidewall 626a in a first half section to fit into an end disk hole 602a and a circular sidewall 626b in a second half section to fit into a corresponding round pocket in the plate hole 606a.

[0194] 12 and 12A relate to a seventh embodiment of a flywheel generally designated "700." This embodiment is similar to the fifth flywheel 500 and its hole spacers 526, except that each spacer 726 in this embodiment has a circular sidewall 726a (similar to a washer) in a first half section and an elliptical sidewall 726b in a second half section to fit into a corresponding pocket in the plate hole 706a.

[0195] The elliptical side walls 726b are larger in diameter than the corresponding end disk holes, however, the spacers are formed (or machined) from a malleable material such that the act of clamping the plate members 706 together in the stack causes the spacers 726 to change shape to fit the end disk holes 702a and / or plate holes 706a.

[0196] It should be noted that the spacers 526, 626 of Figures 10A and 11A may also be formed or machined from any suitable material, including malleable materials.

[0197] 13 and 13A relate to an eighth embodiment of a flywheel generally designated "800". The primary difference from the first flywheel 100 is the shape of the plate members 806. Each plate member 806 includes a peripheral lip 828. The lip 828 is envisioned as an alternative or additional locating means to the spacers described above for locating the stack relative to the plate members.

[0198] The lips 828 are circular and sized to correspond to the outer wall of the end disk 802. In this example, the lips 828 have a substantially U-shaped cross-section at the disk-engaging portion. In some embodiments, each lip 828 can be precision fitted to a corresponding end disk 802.

[0199] Figures 14 and 14A relate to a ninth embodiment of a flywheel generally designated "900". This embodiment is similar to the eighth flywheel 800. However, instead of having a continuous circular lip, each plate member 906 includes an alternative engagement means for the end disk edge. In this example, multiple arm or lip members 928 are provided.

[0200] The four lip members 928 in this embodiment (three of which are visible) are evenly spaced around the plate member 906. The lip members 928 may be formed integrally with the plate member 906. In some embodiments, the lip members 928 are sized to provide a precision fit with the corresponding end disk 902.

[0201] It should be noted that the shape of the plate members shown in FIGS. 13-14A as simple disks is for illustrative purposes only and should not be construed as limiting or indicative of the shape or configuration of the plate members in any flywheel embodiment.

[0202] It will be appreciated that various versions (derivations / variations) of the clamping elements, disks, plate members, spacers, and material layers / films described with respect to Figures 4-14A may be provided in possible combination with the flywheel 100 of Figures 3 and 3A.

[0203] Figures 15A and 15B relate to a tenth embodiment of a flywheel generally designated "1000." Flywheel 1000 in this embodiment has some similarities to flywheel 100 previously described, but differs substantially in that the connection means includes disk-to-disk joints instead of clamps.

[0204] The flywheel 1000 includes a plurality of disks 1002 in a stack 1004. Each disk 1002 is substantially the same size and shape and is aligned along a common axis BB of the flywheel 1000. Each disk 1002 is joined to each of the adjacent disks. None of the disks 1002 require disk holes because the stack does not need to accommodate connecting elements extending between plate members.

[0205] Plate members or cheek plates 1006 are provided at either end of the stack 1004. The plate members 1006 are joined to the ends of the stack 1004. The plate members 1006 may not have a concave stack-facing portion, unlike the plate member of FIG.

[0206] In this embodiment, the plate members 1006 are substantially the same diameter as the disks 1002. Each plate member 1006 is thicker than one of the disks 1002. The outer surface of each plate member 1006 is generally parallel to the surface of the adjacent disk from the radial edge of the plate member 1006 toward the axis BB, approximately one-quarter of the plate member's radius. The thickness of the plate member 1006 then gradually increases as it moves further toward the axis BB.

[0207] A plate member 1006 may connect the lamination stack 1004 to a bearing seat 1050. A cheek plate 1006 also connects and fits the stack 1004 together with an electric machine rotor component 1060.

[0208] Disk-to-disk and disk-to-plate bonding should be accomplished using a bonding material or means that is strong enough to maintain the structural integrity of the flywheel 1000 during high speed rotation. Epoxy resin, with or without toughening additives, is one such example, but should not be construed as the only possible bonding means. It is envisioned that other suitable resins, binders or adhesives may be used. Bonding may optionally be accomplished by, for example, soldering, brazing, or other processing techniques that provide a bonding interface between adjacent disks.

[0209] Disk-to-disk bonding is provided by bond regions 1030 near or at the outer edge of each disk 1002, i.e., at a peripheral region 1032 of each disk 1002. A central region 1034 of each disk (or an area inside each peripheral region 1032) is not bonded to one another. This means that only a portion of the surface of each disk 1002 is bonded to both adjacent disks 1002 (or adjacent disks and adjacent plate members) in the stack 1004.

[0210] With respect to disk thickness in a direction parallel to the flywheel axis BB, the peripheral region 1032 of each disk 1002 is slightly thicker than the central region 1034 of that disk 1002. In Figures 15B and 15C, the thickness difference has been exaggerated for illustrative purposes only. It will be appreciated that this thickness difference may be on the order of a few microns or tens of microns, so long as sufficient space is provided between adjacent central regions 1034 so that they are not in substantial direct contact with one another.

[0211] The peripheral region 1032 of each disk 1002 includes a raised seat (or seating feature) 1032a on each end face, which provides an annular interface region 1030. It will be appreciated that in some embodiments, the seat may be provided on only one end face of each disk.

[0212] Each seat 1032a is substantially annular in shape when viewing the stack from an end view along the flywheel axis BB.

[0213] Each seat 1032a is bonded to a corresponding substantially flat surface or seat 1032a in the peripheral region of an adjacent disk 1002. The thickness of the bond is exaggerated in Figures 15B and 15C for illustrative purposes only.

[0214] The disk-facing peripheral region of each plate member 1006 includes a substantially flat surface or seat 1006b. Each seat 1006b is joined to a corresponding outer seat 1032a of a respective end disk in the stack 1004. A central region of the plate member 1006 is spaced from a central region 1034 of the end disk 1002.

[0215] The seats 1032a, 1006b of the disk and plate member may be formed by stamping or forging the disk 1002 and plate member 1006.

[0216] Figure 15C relates to a variation of the flywheel 1000 of Figures 15A and 15B. In this example, the disk 1002 has substantially the same thickness across its diameter, i.e., it does not have a raised peripheral seat. The plate member 1006 also does not have a raised seat.

[0217] In this example, one or more shims 1036 are provided between adjacent discs 1002 and between each end disc 1002 and the adjacent plate member 1006. The shims 1036 are annular in shape or, where multiple shim pieces 1036 are provided between each pair of adjacent discs, the shims are disposed in an annular fashion between the discs.

[0218] The one or more shims can be made from a metal or other suitable material, such as, for example, a material impregnated with an adhesive. In some embodiments, the shims may be made from a bonding agent, such as solder, that is applied onto a substantially annular region of one or more of the disks 1002 and / or plate members 1006 to be joined.

[0219] The one or more shims are thin enough to provide a small gap or space between the facing central regions of adjacent disks 1002 so that the central regions do not substantially touch. The shims at the ends of the stack 1004 similarly provide a small gap or space between the outwardly facing central region of each end disk 1002 and the stack-facing central region of the plate member 1006 so that the central regions do not substantially touch. In Figure 15C, the thickness of the shims is exaggerated for illustrative purposes only.

[0220] It will be appreciated that although minor contact may occur between adjacent central regions, the present invention is intended to minimize the extent of disk-to-disk contact so that contact is primarily at the periphery of each disk.

[0221] Each shim or set of shims 1036 is bonded to opposing peripheral regions of an adjacent pair of disks 1002. That is, a bonding area 1030 is provided on either side of one or more shims to provide a shim-to-disk bond. A first side of the shim is bonded to a first peripheral region of a first disk. An opposing second side of the shim is bonded to a second peripheral region of a second disk. The bonding means / materials are similar to those in FIG. 15B, but can be tailored to the shim material to maximize bond strength.

[0222] Similarly, one or more shims 1036 are bonded to the facing peripheral regions of each end disk 1002 and the adjacent plate member 1006. A first face of the, or each, shim is bonded to the outer periphery region of the end of the stack 1004. An opposite second face of the shim is bonded to the stack-facing peripheral region of the plate member 1006.

[0223] It will be appreciated that both the attachment means described in relation to Figures 15B and 15C may be provided in a given flywheel, if desired.

[0224] 16 relates to an eleventh embodiment of a flywheel generally designated "1100". The flywheel 1100 in this embodiment has similar features / functions as the flywheel 100 described above with respect to the first embodiment, but differs substantially in that the connection means are provided in contact (specifically indirect contact) with some or all of the disk holes 1102.

[0225] It will be understood that the various configurations of clamping elements, discs, plate members, spacers, and material layers / films described with respect to Figures 4-14A may be provided in the flywheel 1100 to the extent selected features / functions are not inconsistent hereinbelow.

[0226] A number of supports or space-filling elements 1138 are provided, each for supporting one of the clamping elements 1114 in the stack 1104. The supports 1138 can be thought of as sheaths or sleeves that fit snugly around the clamping elements 1114 and inside the series of disk holes 1102.

[0227] Each plate member 1106 has a recess 1106c around each of its plate holes 1106a. Each recess 1106c is configured to engage an end of a respective one of the supports 1138.

[0228] FIG. 16A shows an elongated sleeve 1138. An end wall 1138b of the sleeve 1138 extends from the stack into each recess 1106c of the plate member 1106 of FIG. 16. The sleeve 1138 has an outer wall contour 1138a that is substantially elliptical to match the substantially elliptical inner wall contour of each disk hole in the stack 1104. The sleeve 1138 is rigid in this embodiment. A bore 1140 is provided through the center of the support 1138 for receiving and supporting a clamping element.

[0229] The support 1138 can be thought of as an elongated, double-ended variation of the spacer of FIG. 11A, but it is understood that it is designed to fit through all of the disk holes and along the length of the clamping element.

[0230] 16B shows an end view of an alternative support 1138'. In this example, a series of elongated channels 1142 are provided along some or all of the length of the support 1138'. These channels allow the support 1138' to be substantially flexible along some or all of its length and to minimize its mass.

[0231] Channels 1142 are provided on the periphery of sleeve 1138'. These channels do not intersect with bore 1140 that receives the clamping element. Channels 1142 can be formed, for example, by molding sleeve 1138'.

[0232] The channels 1142 are of different sizes. Each channel 1142 has a generally cylindrical bore. The diameter of the bore is selected such that the circumference of the bore does not extend beyond the end wall 1138b at all, as seen in FIG. 16B. The size of the bore may be varied in other embodiments to selectively adjust the stiffness or flexibility of the support sleeve 1138'.

[0233] It will be appreciated that multiple cavities may be provided within the body of the support 1138, 1138' to achieve a similar effect in other embodiments. The arrangement of the channels / cavities is not limited to that shown in Figure 16B, and other suitable arrangements may be provided.

[0234] 17 and 17A relate to a twelfth embodiment of a flywheel generally designated "1200." Flywheel 1200 in this embodiment is similar to flywheel 100, but differs substantially in that connection means are provided in contact (e.g., indirect contact) with some or all of the disk holes 1202.

[0235] However, unlike the eleventh flywheel 1100, this flywheel 1200 does not include a sleeve in the space between the connecting element and the disk hole. The connecting element is provided with a separate support means.

[0236] Each clamping element 1214 includes a conduit 1244. Each conduit includes an axial inlet 1246a through the end of the clamping element 1214 and a radial outlet 1246b (or in some embodiments, multiple radial outlets) that opens into a sidewall of the clamping element 1214. The outlet 1246b is provided from the inner end of the conduit 1244 (i.e., the pointed end shown in FIG. 17A).

[0237] One or more conduits 1244 allow a fluid material 1248 to be introduced, e.g., injected under pressure, through each clamping element and into the space around the clamping elements 1214. The fluid material flows into the recesses 1206c of the plate holes 1206a as well as between the disk holes 1002a and the clamping elements 1214. Thus, the fluid material may be introduced after the flywheel 1200 is assembled.

[0238] In some embodiments, the fluid material melts and cools to form solid supports or spacers around some or all of the clamping elements, while in other embodiments the fluid material solidifies / hardens to form a similarly shaped solid support that provides support that stretches across the stack and into the plate members.

[0239] The material may be a thermoplastic or thermoset plastic (optionally containing reinforcing fillers as applied). It may also be a low melting point metal or alloy, such as a solder. Ideally, the melting point of the material should be below 600°C.

[0240] The above examples are provided for illustrative purposes only, and various changes and modifications will be apparent to those of ordinary skill in the art without departing from the scope of the invention, as defined by the claims.

Claims

1. A flywheel, a plurality of disks arranged in a stack, the plurality of disks including at least first and second end disks at opposite ends of the stack, each disk including a central region and a peripheral region surrounding the central region, the peripheral region adjacent a periphery of the disk; first and second plate members disposed on opposite ends of the stack; and joining means for joining only a portion of each disk in the stack to a respective adjacent disk, including joining adjacent peripheral regions of the adjacent disks to one another, and joining each of the first and second plate members to the first and second end disks of the stack, respectively.

2. 2. The flywheel of claim 1, wherein the peripheral regions of some or all of the disks are at least slightly thicker than the central regions of the disks to space adjacent central regions of adjacent pairs of the disks.

3. 2. The flywheel of claim 1, wherein the peripheral region of each of the discs includes a substantially flat surface or seat on one or both sides of each disc, the substantially flat surface or seat being joined to a corresponding substantially flat surface or seat on the peripheral region of an adjacent disc.

4. 2. A flywheel as claimed in claim 1, wherein said joining means comprises or consists of an annular joining area between each pair of adjacent discs in said stack.

5. 10. The flywheel of claim 1, wherein one or more shims or seating elements are provided for some or all of the adjacent pairs of disks in the stack.

6. 6. A flywheel as claimed in claim 5, wherein the or each shim or seating element is joined to adjacent peripheral regions of adjacent pairs of the disks, with adjacent central regions of the adjacent pairs of disks spaced apart.

7. A flywheel according to claim 5, wherein the or each shim comprises a metal or metal alloy.

8. 8. The flywheel of claim 7, wherein the metal or metal alloy is or includes one of steel, aluminum, or titanium.

9. A flywheel according to claim 5, wherein the or each shim is substantially annular in shape.

10. 2. The flywheel of claim 1, which does not include clamping means for clamping said discs together in said stack.

11. 11. The flywheel of claim 10, wherein the stack of discs does not contain clamping elements extending between the plate members.

12. 2. The flywheel of claim 1, wherein the disc does not include disc holes for connecting elements.

13. The flywheel of claim 1 , wherein the plate member does not include one or more plate holes for connecting elements.

14. 2. The flywheel of claim 1, wherein the joining means comprises an adhesive such as an epoxy or engineering adhesive that will withstand flywheel rotation.

15. 2. The flywheel of claim 1, wherein the facing central regions of adjacent discs are spaced apart when the flywheel is stationary.

16. 4. The flywheel of claim 3, wherein the contact area between adjacent disks is less than 100% of the disk-facing area of ​​a given disk.

17. A flywheel assembly including one or more flywheels according to any one of claims 1 to 16, A flywheel assembly wherein the or each said flywheel is mounted to or to a drive assembly which facilitates rotation of the or each said flywheel to store energy in or distribute energy from at least one of the flywheels.

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