flywheel

Abstract

The present invention relates to a flywheel 100. The flywheel 100 comprises a disk 102 organized into a stack 104, each disk having a through disk opening, and first and second plate members 106 positioned at opposite ends of the stack, and connecting means for clamping the plate members together to the outside of the stack of disks. One or both of the plate members have a through plate opening for alignment with a series of disk openings that penetrate the stack. One, some or all of the disk openings include a circular disk opening 120 for accommodating through the connecting means, and non-circular disk openings 122a spaced from the periphery 130 of the disk and slots 122b extending from the periphery 130 of the disk to reduce stress on or around the circular disk opening when the flywheel rotates. The circular disk opening is positioned between a pair of non-circular disk openings and / or slots.

Description

Technical Field

[0001] The present invention relates to flywheels, and more particularly, but not limited to, flywheels for use in energy storage and / or deployment, and more particularly, but not limited to, flywheels for use in energy infrastructure, and to flywheel disks for flywheels.

Background Art

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

[0003] The electromechanics are typically used to accelerate the inertial element to store energy or to decelerate the inertial element to release energy. The inertial element conserves energy by its angular momentum, and the faster the rotation, the more energy is conserved, and the energy conservation is proportional to the square of the angular velocity.

[0004] To store a high level of energy (i.e., to have a high capacity for energy storage), the inertial element must operate at a speed that exceeds a very high peripheral velocity, typically the speed of sound (measured in air under standard atmospheric conditions, in contrast to the conditions within the flywheel casing). Therefore, the structure of the inertial element in an energy storage flywheel is significantly different from the structure of the inertial element in a flywheel designed for other applications.

[0005] For example, a significantly different application is to provide a flywheel mounted on the crankshaft of an internal combustion engine to smooth intermittent torque and prevent the engine from stalling. Flywheels used for such smoothing typically have rotor velocities on the order of tens of meters per second (relatively low energy capacity), while energy storage flywheels have rotor velocities on the order of hundreds of meters per second (relatively high energy capacity). As a result, flywheels for such smoothing applications do not experience the very high stresses that energy storage flywheel types must withstand. A further distinction is that energy storage flywheels can hold energy for periods of several seconds, minutes, or hours and then release that energy when needed. In the case of flywheels used for torque smoothing, a small amount of energy is passively transferred in and out of the flywheel in sync with the pulsations of the internal combustion engine.

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

[0007] The main design challenges for inertial elements used in the energy storage class of flywheels are how to withstand the high centrifugal stresses induced by high peripheral velocities, while simultaneously maximizing the safety of the energy storage flywheel during operation.

[0008] One approach is to make the risk of rotor structure failure negligible, that is, to ensure that the flywheel inertia elements do not suffer material failure. This can be achieved by using ultra-high-quality materials and employing non-destructive testing methods to guarantee material quality and carefully monitor rotor usage, especially the number of completed operating cycles. While such techniques have been developed by the aerospace industry, the required materials and the monitoring performed are costly and time-consuming.

[0009] Another approach is to accept that the inertial element may fail during operation, which is a rare occurrence. However, any fragment ejected from the inertial element (which has high linear kinetic energy) must be contained by a casing to avoid damage to the properties, or, in more serious cases, human casualties. This can be achieved at a relatively lower cost than the first approach described above, as it allows for the use of lower-cost materials in mass production, requires less rigorous monitoring, and thus lowers maintenance costs. However, to ensure safety, the mass of the containment element must be substantially greater than the mass of the inertial element being contained, with experts recommending a value of approximately 10 times the mass of the inertial element. The size and cost required to achieve such safety means that the primary practical implementation is to place an energy storage flywheel (typically with a monolithic steel inertial element) in an underground bunker. However, installation costs remain high, and flexibility in how the stored energy can be deployed is reduced.

[0010] A third approach involves constructing the inertial element from a fibrous composite material, which can result in a material that is substantially tougher than the materials used in the approaches described above. Traditionally, composite materials were thought to always fail in a relatively gentle manner, because, theoretically, the inertial element should break down into many smaller particles that can be more easily contained using a lighter and cheaper casing than, for example, the second approach. However, some failure modes of the inertial element are still extremely violent due to the higher energy storage levels, and can generate high pressure inside the casing. Therefore, flywheel energy storage systems that use composite materials in the inertial element are also typically placed in very thick and heavy containment vessels or underground bunkers for safety reasons.

[0011] A fourth approach is to use metallic materials for the inertial elements. While typically steel, instead of using a monolithic cylindrical design, the inertial elements can be assembled from stacks of thin disks or laminates. Since the highest stresses in a rotating disk are tangential and radial, using a series of thin disks means the rotor can operate at the same speed as (or even faster than) a monolithic cylinder. In fact, stresses can actually be lower with such an approach because axial stresses are reduced. In the event of a structural failure in the inertial elements of such a structure, only a portion of the entire inertial element will be discharged. Therefore, this approach substantially reduces the level of containment required for the safe operation of the flywheel, allowing for the use of a much lighter casing. That is, no thick, heavy casing or bunker installation is required, significantly reducing costs, facilitating ground-based flywheel installation, and resulting in a compact configuration.

[0012] A key consideration in this fourth approach is to ensure that a failure in one disk does not propagate to adjacent disks (and disks beyond that), otherwise a cascading failure may occur, resulting in the ejection of debris from two or more disks. In addition, the disks / laminated stack must be securely fixed to each other within the stack, and the stack must be connected to the shaft so that the rotor can be positioned within the bearing.

[0013] From a commercial standpoint, it should be noted that the ability to manufacture flywheel rotors at low cost is extremely important. Otherwise, for energy storage applications where flywheel-based systems are the ideal energy storage solution, alternative energy storage methods such as electrochemical batteries and ultracapacitors would remain cheaper, even if they offer less practical solutions.

[0014] US7267028 (Gabrys) discusses laminated flywheels in which the central hole of the disc is recognized as causing high stress, reduced peripheral velocity, and decreased performance. In addition, thinner steel may offer preferable high-strength properties compared to thick monolithic cylinders.

[0015] Gabrys discusses two methods for connecting a disk and a coupling means to a shaft for a bearing. One of these methods will be described with respect to Figure 12 of US7267028, which is substantially reproduced in Figure 1 (Prior Art) of this application. This first method relies on joining the surfaces of the disk (1) using adhesive, soldering, or brazing (2). The coupling means and the shaft (3) are also joined.

[0016] The problem with this approach is that the joint is subjected to extremely high stress, requiring a very strong bonding material to prevent joint failure. However, if the bond is strong, a crack that starts in one laminate can propagate to other laminates, leading to undesirable cascading failure. As a result, a benign case where only one laminate fails is not realized.

[0017] The reason for the high stress on the joint is explained below with reference to Figure 1 of this application (prior art), which is annotated in relation to Figure 12 of Gabrys for the sake of clarity.

[0018] When the disk rotates at high speed, the maximum radial and tangential stresses occur in the region around the center of the disk. This reduces the axial thickness of the disk by an amount indicated by Δt, due to the effect of Poisson's ratio. The cross-sectional shape of each disk during rotation is shown by the dotted line, and this deformation is exaggerated for illustrative purposes. Since the joint is relatively thin, it is difficult to absorb the effect of the disk being pulled apart in the bore unless the joint is very strong.

[0019] The shaft connection mechanism presents an additional problem: the diameter of the small disk is smaller than that of the main disk. The radial elongation of the upper small disk, denoted by Δr2, is smaller than the elongation Δr1 of the adjacent main disk. This creates substantial shear stress in the connection, and therefore, the joint must be strong enough to resist it.

[0020] On the other hand, with a strong bond, for the reasons mentioned above, a crack in one disk cannot avoid cascading failure. In this case, the crack is most likely to form around the center of one disk. As it grows radially outward across the disk, the stress in two adjacent disks increases because the load is transmitted to these disks through the strong bond. Since these adjacent disks are already operating under high stress, this increase in local stress can cause cracks in the adjacent disks. This sequence is repeated until some, if not all, of the disks crack, resulting in a highly undesirable multi-disk failure mode.

[0021] Finally, adding a stepped shape (see Figure 13 by Gabrys) can potentially strengthen the joint, but it would place high stress on the disk at the corners of the stepped shape on the female side of the mating. Manufacturing the stepped shape is also expensive.

[0022] US10138980 (Sanders et al.) attempts to solve some of the aforementioned problems by using spigots on each disc and collars between each joint. However, these joints require precision manufacturing. This may be feasible for the limited production of very heavy flywheels as described by Sanders et al., but it would be very costly for mass production of flywheels. This structure may also be somewhat unstable in use, given that the joints have small diameters and the discs are not mechanically locked together.

[0023] EP2759043 (Pullen) describes a laminated flywheel structure in which bolts can be inserted into disks through specially shaped openings to reduce stress at the openings. FIG. 2 of the present application (Prior Art) shows FIG. 14 of EP2759043, where 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 formed openings in the disks (12) and are stabilized at a predetermined position within the holes by inserts. The disks having the openings of EP2759043 are intended to operate at the same speed as disks without openings. However, to ensure the stability of the flywheel, this structure requires precise fitting between its components, which is costly. The use of specially shaped non - circular openings has been shown to significantly improve the performance of laminated flywheels based on clamping means passing through circular laminates. However, this requires the use of axially oriented spacers inserted inside the openings, and the spacers have round openings through which bolt - tightening means can be inserted.

[0024] An object of the present invention is to reduce, or substantially avoid, at least some of the above problems, particularly (but not limited to) a flywheel with reduced storage requirements and, preferably, a simpler structure with fewer parts that can be manufactured at a relatively low cost.

Prior Art Documents

Patent Documents

[0025]

Patent Document 1

Patent Document 2

Patent Document 3

SUMMARY OF THE INVENTION

[0026] According to a first aspect of the present invention, a flywheel is provided. The flywheel comprises 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 through disk apertures, 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 apertures therethrough for alignment with a corresponding series of the disk apertures through the stack, connection means for clamping the first and second plate members together outside the stack of disks, one, some, or each of the plurality of disk apertures including a first set of circular disk apertures for receiving through the connection means, a second set of apertures for reducing stress in or around the circular disk apertures during flywheel rotation, the second set of apertures including either or both of (i) non-circular disk apertures and / or (ii) slots extending from the peripheral edge of each disk, each of the non-circular disk apertures and / or the slots being disposed (or distributed) between a predetermined pair of the circular disk apertures.

[0027] According to a related aspect of the present invention, there is a flywheel according to claim 1. Any features are described in the dependent claims.

[0028] Thereby, the flywheel can operate at high speed while reducing the risk of catastrophic failure. The flywheel according to the present invention is subject to less of the high stress normally associated with circular disk apertures while maintaining a simple design with fewer parts (i.e., spacers may not be required).

[0029] The circular disk opening is provided to receive connecting means. Each connecting means may have a circular cross-section. Each connecting means can be received through the circular disk opening without requiring additional spacers. Additional spacers may otherwise occupy space within the non-circular disk opening to accommodate the difference in shape between the non-circular disk opening and the connecting means.

[0030] Additional non-circular disk openings and / or slots may be provided on both sides of the circular disk opening to relieve stress on the circular disk opening.

[0031] "Disk opening" is intended to mean the opening of the disk.

[0032] The term "slot" should be interpreted as meaning a groove or void in the otherwise circular cross-section of each disk. Each slot may extend almost entirely through each disk. The slots can provide voids around the periphery of the disk to accommodate the expansion of the periphery during flywheel rotation. The plate members can be considered as end plates.

[0033] The statement that a non-circular disk opening and / or slot is "located between" a given pair of circular disk openings can be interpreted as meaning that, when those openings are examined sequentially or stepwise along the circumference, the pair of circular disk openings are positioned angularly forward and angularly backward, respectively, with respect to the given non-circular disk opening and / or slot.

[0034] If slots are provided, and at least some of them extend inward from the periphery, the periphery of each disk can be considered an interrupted periphery. The periphery may have a similar overall shape in a plan view, for example, substantially circular, but it may also have multiple arcs or arc portions located between pairs of slots.

[0035] The non-circular disk opening is elliptical, oval, elliptical-like, or oval-like in shape. Throughout this specification, the examples of the term “elliptical” are intended to encompass any of these four terms and, in particular, not to mean a shape that is mathematically elliptical.

[0036] The term "ellipse" is used to describe a shape that is generally based on a circle stretched along at least one axis.

[0037] Each non-circular disk opening may have a first width. The first width may extend along a first axis passing through the center of the non-circular disk opening. The first width can be considered as the maximum width or diameter.

[0038] Each non-circular disk opening may have a second width. The second width may extend along a second axis perpendicular to the first axis and passing through the center of the non-circular disk opening. The second width can be considered as the minimum width or diameter. The first width may be greater than the second width.

[0039] Non-circular (or elliptical) disk openings may be located near the periphery of the disk. That is, they are at least closer to the periphery than to the center of the disk, preferably within approximately 25% of the outer edge of the disk radius.

[0040] The elliptical disk opening tends to become circular during flywheel rotation. The elliptical disk opening minimizes stress on the circular disk opening during flywheel rotation.

[0041] The flywheel may be of any suitable size. That is, the exemplary embodiments described herein are not strictly limited to any particular scale and can be scaled up or down as required for a specific application.

[0042] The first width may be greater than the diameter of each circular disk opening. The second width may be equal to the diameter of each circular disk opening.

[0043] The first width may be approximately twice the length of the second width.

[0044] The second width may be approximately the same length as the adjacent slot (if both non-circular holes and slots are provided).

[0045] The first width, the second width, and (if provided) the slots may have a length ratio of 2:1:1 (or simply 2:1 if adjacent or neighboring slots are not provided).

[0046] Each slot in the second set of non-circular openings may have a width in the tangential direction of the disk (or perpendicular to the radius of the disk). The width of each slot may be less than half the diameter of a given circular disk opening.

[0047] At least one of the circular disk openings, non-circular disk openings, and slots may be positioned on a pitch circle. That is, the disk openings and / or slots may be positioned on (or centered on) a virtual circle that is smaller than the periphery of each disk and concentric with it.

[0048] Circular and non-circular disk openings may be arranged alternately along the periphery of the disk. The arrangement of disk openings may form a repeating arrangement along at least a portion of the periphery of multiple disks. The number of circular disk openings may be equal to the number of non-circular disk openings and / or slots.

[0049] In some flywheel discs, the ratio of circular disc openings to non-circular disc openings may be many to one, for example 2:1, or other ratios (greater than 1):1. Two circular disc openings may be provided between a pair of non-circular disc openings. The slots and non-circular disc openings may be provided in a rotationally symmetric arrangement.

[0050] In some flywheel discs, the ratio of circular disk openings to non-circular disk openings may be one to many, for example, 1:2, or 1:(greater than 1) or other ratios. Two non-circular disk openings may be provided between a pair of circular disk openings. The slots and non-circular disk openings may be provided in a rotationally symmetrical arrangement.

[0051] Circular disk openings may be arranged at equal distances along the periphery of each of the multiple disks. Non-circular disk openings and / or slots may each be arranged at equal distances along the periphery of each of the multiple disks. Circular and non-circular disk openings may each be arranged at equal distances along the periphery of each of the multiple disks.

[0052] The arrangement of disk openings and / or slots is intended to help minimize the maximum stress that is expected to occur, as the maximum stress could limit the flywheel rotation speed.

[0053] Each non-circular disk opening may be spaced from the periphery of the host disk by a distance equivalent to the second width of each circular disk opening.

[0054] The circular disk opening does not need to contact or intersect with the periphery of the host disk.

[0055] At least one of the non-circular disk openings may be connected to or intersected by at least one slot. The slot may connect to the non-circular disk opening at a substantially central position.

[0056] Each noncircular aperture and slot, when connected or in appropriate relative position, can be considered substantially T-shaped or may provide a stress-relieving opening that is substantially T-shaped; that is, it has a T-shape. The "root" (bottom edge) of the T-shape can be in contact with the periphery of the disk.

[0057] It will be understood that the shape can be roughly T-shaped. If the non-circular opening is elliptical or similar in shape, the branches of the T may appear to "bulge" (in plan view), but the overall shape will still be readily apparent as T-shaped.

[0058] In some embodiments, some or all of the slots may not connect to a non-circular disk opening, but may be located elsewhere on the disk (preferably still on the periphery).

[0059] Adhesive may be provided between multiple flywheel discs to prevent relative movement of the discs.

[0060] At least one connecting means may contact the side wall of at least one circular disk opening (or the side walls of a series of aligned disk openings that the connecting means closes). The diameter of the circular disk opening may substantially coincide with the diameter of the cross-section of the connecting means. In other words, there may not be a gap between the side wall of the disk opening and the connecting means. To provide a simpler structure with fewer parts, spacers may not be required.

[0061] The connecting means may include one or more rods. For example, the connecting means may include one or more bolts or threaded studs.

[0062] Each rod may be substantially solid or tubular (i.e., hollow inside).

[0063] Each connecting means may include one or more neck portions for reducing stress on the connecting means and the plate member.

[0064] The connecting means may have a reduced diameter at the neck. The neck portion may be positioned in one of the corresponding plate openings of the first plate member.

[0065] Each neck portion may be entirely received by the plate member. The neck portion may be positioned adjacent to the tip of the rod, or it may be inserted from the tip. The tip of the rod may be positioned within the plate member.

[0066] The neck portion can reduce the mass and / or bending stiffness of the connecting means. The neck portion (each neck portion) can reduce stress in any one or more of the connecting means itself, the plate member, and / or the laminate adjacent to or near the plate member.

[0067] The connecting means may comprise one or more hollow portions. Each hollow portion may be located at the head or tip of a rod / threaded stud.

[0068] The hollow portion can reduce the mass of the connecting means and the load induced during flywheel rotation. The hollow portion and / or neck portion can alleviate the pressure on the threaded stud during flywheel rotation.

[0069] The arrangement of disk openings on a given disk may have rotational symmetry with respect to the center of the disk, and this symmetry may be at least twice symmetric or multiple times symmetric, depending on the number of circular or non-circular openings or slots provided on the disk.

[0070] The width of one, some, or all of the circular disk openings may be at least approximately 3% of the disk's diameter.

[0071] The width of one, some, or all of the circular disk openings may be at most approximately 10% of the disk's diameter.

[0072] The width of one, some, or all of the circular disk openings may be approximately 5% of the disk's diameter.

[0073] A flywheel can be an energy storage flywheel. A flywheel can also be an energy infrastructure flywheel. A flywheel can be designed to be installed within (or provided as part of) a flywheel energy storage system for energy infrastructure.

[0074] The types of flywheels described herein may not be, in particular, types of flywheels provided for internal combustion engines. For example, they may not be the types used in automobiles or as part of starter mechanisms or motors.

[0075] This flywheel can have a kinetic energy storage capacity of at least 100 kilojoules (kJ) when in use. Preferably, this flywheel can have a kinetic energy storage capacity of at least 200 kJ. This flywheel can have a kinetic energy storage capacity of at least 350 meters / second (ms) when in use. -1 It may be possible to achieve a periphery speed of )

[0076] A flywheel (especially its inertial element) can have a minimum stored energy of 25 kJ per kilogram when in use.

[0077] Each disc can be considered an inertial element (or stacking element) of the flywheel. Each disc is configured or structured for a stack that stores the majority of the kinetic energy in the flywheel during rotation.

[0078] One, some, or all of the disks may be substantially Laval or rimmed-Laval in shape, or may have a substantially Laval portion (which may be the central portion of the disk). In other words, one, some, or all of the disks may have a thin (or thinner) portion or annular region relative to the rest of the disk.

[0079] This thin portion may have an asymmetrical cross-section when considering a cross-section radially outward from the central longitudinal axis of the disk (i.e., the assumed axis of rotation) toward the periphery of the disk. The thin portion may extend around the entire circumference of the disk.

[0080] The thin portion may be adjacent to the peripheral region of the disk. The thin portion may be said to be the radially inner portion of the peripheral region of the disk, or the radially outer portion of the central region of the disk. When referring to the radially inner and radially outer portions, it is intended to be interpreted with respect to the central longitudinal axis of the disk (the assumed axis of rotation of the disk when assembled on a flywheel).

[0081] A flywheel may be mounted to a drive assembly that propels the rotation of a flywheel in order to store or extract energy from at least one of a group of flywheels.

[0082] According to a second aspect of the present invention, a flywheel disc for a flywheel is provided. This flywheel disc is configured to include a plurality of disc openings, the plurality of disc openings are A first set of circular disk openings for accommodating through connecting means, A second set of openings for reducing stress in or around the circular disk openings when the flywheel rotates, comprising (i) non-circular disk openings and / or (ii) slots extending from (or near) the periphery of each disk, wherein each of the non-circular disk openings and / or the slots is positioned between a predetermined pair of circular disk openings.

[0083] According to a related aspect of the present invention, there is a flywheel disc as described in claim 20.

[0084] The advantages are the same as those described in relation to the first aspect of the present invention. Any feature or combination of features presented in relation to the first aspect of the present invention may also be provided in relation to the second aspect or related aspects of the present invention.

[0085] According to a third aspect of the present invention, a flywheel is provided. This flywheel is A plurality of disks arranged in a stack, the stack including at least first and second end disks at both ends, each of the plurality of disks including a plurality of disk openings through which the disks pass, First and second plate members positioned at opposite ends of the stack, wherein one or both of the first and second plate members include a plurality of plate openings through which a corresponding series of disk openings passing through the stack are located, A plurality of rods for clamping the first and second plate members together to the outside of the stack of discs, each of which is of a certain length, is positioned through a corresponding series of the disc openings, and one, some, or all of the rods have a first neck (reduced diameter) portion located in one of the corresponding plate openings of the first plate member.

[0086] The neck portion of the rod can substantially reduce stress in any one or more of the connecting means itself, the plate member, and / or the laminate adjacent to or near the plate member. This reduces the risk of catastrophic flywheel failure and provides a more reliable flywheel at a relatively low cost.

[0087] The rod may be (or part thereof) a threaded bolt or stud.

[0088] Part or all of the rod may each have a second neck portion. The second neck portion may be located in one of the corresponding plate openings of the second plate member. The second neck portion may be positioned through a stack of discs. The second neck portion may be on the opposite side of the rod, stack, or plate member from the first neck portion.

[0089] The neck portion can be considered as a tapered neck or a portion with a narrowed diameter / cross-section. The neck portion can reduce the mass and bending stiffness of the rod. The neck portion can reduce the stress on the rod and plate members. The neck portion can reduce the stress on the disk positioned adjacent to or near the plate member.

[0090] Each rod may include at least one hollow section. The at least one hollow section may be located at one, some, or all of the ends of the rod. A rod may include a hollow section at each opposite end of the rod. The hollow section may be located at at least one of the plate members.

[0091] The hollow section and / or neck section can relieve pressure on the rod when the flywheel rotates.

[0092] According to a fourth aspect of the present invention, a flywheel assembly is provided comprising one or more flywheels according to the first or third aspect of the present invention, or one or more discs according to the second aspect, wherein the flywheel (each flywheel) is mounted to a drive assembly for propelling the rotation of the flywheel (each flywheel) in order to store energy in or extract energy from at least one flywheel.

[0093] Each aspect of the present invention may include one or more features presented in relation to any other aspect of the present invention. [Brief explanation of the drawing]

[0094] To better understand the present invention and to more clearly illustrate how it can be implemented, the drawings are provided as mere examples. [Figure 1] Side view of the first prior art flywheel device, extracted from US7267028. [Figure 2] A side view including a cross-section of the second prior art flywheel device, extracted from EP2759043. [Figure 3] A side view including a cross-section of a first embodiment of the flywheel according to the present invention. [Figure 4] A top view of the first embodiment of the flywheel disc shown in Figure 3. [Figure 5] Figure 3 is a side view of the flywheel, including a partially enlarged cross-section. [Figure 6] A partial side view including a cross-section of a second embodiment of the flywheel according to the present invention. [Figure 7] A top view of a second embodiment of a disc for a flywheel according to the present invention. [Figure 8] A top view of a third embodiment of a disc for a flywheel according to the present invention. [Modes for carrying out the invention]

[0095] Figures 1 and 2 relate to prior art devices described in the background information section.

[0096] Referring first to Figure 3, the flywheel according to the present invention is shown as "100" overall.

[0097] The flywheel 100 is designed for use in kinetic energy storage, and can be used in conjunction with a suitable electric motor-generator or mechanical drive or shaft spigot (or other suitable type of drive means), with any suitable bearings required to provide a means for storing electrical energy.

[0098] The flywheel 100 has many possible applications, including, but is not limited to, local grid boosting for fast-charging electric vehicles, uninterruptible power supplies, trackside rails, demand-side management, and electric grid services, one or more of these. The flywheel 100 can also be installed on vehicles with electric propulsion systems, such as cars, trucks, buses, trains, airplanes, or boats.

[0099] The flywheel 100 may also be used to provide a kinetic energy reservoir that can mechanically transmit stored energy to assist in the acceleration of the vehicle and extract kinetic energy that would otherwise be lost. The structure of the flywheel 100 will be described primarily in terms of the flywheel in a stationary state unless otherwise specified.

[0100] The flywheel 100 includes a plurality of disks 102 (also called a stack). In this embodiment, 14 disks 102 are shown, but it will be understood that in other embodiments, any suitable number of disks may be provided, provided that at least first and second end disks are present.

[0101] In this embodiment, disk 102 has a substantially circular contour. The centers of disk 102 are aligned in the direction of a common longitudinal axis AA, providing a stack 104 of disks. In this embodiment, the stack 104 is substantially cylindrical.

[0102] Stack 104 can be thought of as providing the inertial elements for the flywheel 100. Stack 104 can also be considered a stacked stack.

[0103] In this embodiment, each disc 102 may be made of steel, but in other embodiments, another suitable metal, alloy, or composite material may be used.

[0104] Each of the disks 102 in this embodiment has a plurality of circular disk openings 120. Each disk 102 in the stack is substantially the same in this embodiment and preferably has a tolerance on the order of a few microns or tens of microns.

[0105] A pair of plate members 106 (also called teak plates) are positioned at both ends of the stack 104. The plate members 106 are fixed or clamped together to the outside of the stack 104. In this embodiment, each plate member 106 has a diameter smaller than the diameter of the disc stack 104.

[0106] The cheek plate 106 connects the stacked assembly 104 to the bearing landing 150. The cheek plate 106 also allows the stacked assembly 104 to be connected to or mated with (or more broadly, provided operably engaged with) an electromechanical rotor component or a mechanical drive component 160. This enables the use of the flywheel in energy recovery and / or utilization.

[0107] The connecting means secure the plate member 106 together to the outside of the disk stack. In this embodiment, multiple connecting means are provided. The connecting means in this embodiment include multiple threaded studs 114, which will be described in more detail with reference to Figure 6.

[0108] The circular disk openings 120 are shown on the exemplary disk in Figure 4. In this embodiment, each disk 102 has 12 circular disk openings 120. The circular disk openings 120 are arranged along (and inward from) the periphery 130 of the disk 102. In this embodiment, the circular disk openings 120 are arranged on a pitch circle 170, but it will be understood that in other embodiments, other arrangements or distributions of the circular openings may be provided. In this embodiment, the circular disk openings 120 are arranged at equal intervals.

[0109] In this embodiment, the minimum distance between each circular disk opening 120 and the periphery 130 is approximately equal to the diameter of the circular disk opening 120. The opening is sized appropriately to accommodate the connecting means, and no specific limitations on the absolute size or dimensions of the opening should be inferred, as long as it does not significantly affect the structural integrity of the disk. Naturally, the distance from the periphery to the circular opening may be changed as needed, but preferably the center of the circular opening is located closer to the periphery than to the center of the disk.

[0110] The threaded studs 114 have a substantially circular cross-section. Each threaded stud 114 is received into each of the circular disk openings 120. The cross-section of the threaded studs 114 substantially coincides with the cross-section of the circular openings 120. That is, a loose fit is applied between the pair of threaded studs 114 and circular disk openings 120. The outer surface of each threaded stud 114 is in contact with the inner surface of each circular disk opening 120. This configuration is advantageous because no spacers are required between the connecting means and the circular disk openings 120. The invention as claimed provides a simpler design with a reduced number of required parts.

[0111] In some embodiments, an adhesive may be provided between the flywheel discs 102, for example, to prevent relative motion between them and / or to improve thermal conductivity. The adhesive should not be too strong in order to mitigate crack propagation between the discs.

[0112] In some embodiments, the threaded stud 114 can be replaced by other fastening means, such as a bolt with a nut or rivet.

[0113] The non-circular disk openings 122a are arranged to penetrate the flywheel disk 102. A predetermined pair of two non-circular disk openings 122a are positioned on either side of a predetermined circular disk opening 120. In this embodiment, the number of non-circular disk openings 122a is equal to the number of circular disk openings 120 (i.e., 12 non-circular disk openings 122a are provided).

[0114] The non-circular disk openings 122a are arranged at equal intervals around the entire circumference of the disk. Both the circular disk openings 120 and the non-circular disk openings 122b are arranged at equal intervals around the entire circumference of the disk.

[0115] In this embodiment, the non-circular disk opening 122a is elliptical. The elliptical shape is broadly preferred because it tends to become circular as the flywheel disk 102 rotates. It will be understood that in other embodiments, other shapes that tend to become circular as the flywheel rotates may be used. For example, the non-circular disk opening 122a may be formed from two or more intersecting circular openings.

[0116] The minimum distance between each non-circular disk opening 122a and the peripheral edge 130 is substantially equivalent to the minimum distance between the circular disk opening 120 and the peripheral edge 130. The non-circular openings 122a may lie on the same pitch circle as the circular openings.

[0117] Naturally, the distance of the non-circular opening from the periphery can be varied as needed (provided that stress on the circular opening is reduced), but preferably, the center of the non-circular opening 122a is positioned closer to the periphery than to the center of the disk.

[0118] The non-circular disk opening 122a has a first width or diameter tangentially to the flywheel disc 102. The first width is approximately twice the diameter of the circular disk opening 120. The non-circular disk opening 122a has a second width or diameter radially to the flywheel disc 102. The second width is substantially equivalent to the diameter of the circular disk opening 120. No specific limitation on the absolute size or dimensions of the non-circular opening 122a should be inferred unless the opening is appropriately sized to reduce disk stress during flywheel rotation and does not significantly affect the structural integrity of the disk.

[0119] Slots 122b are provided throughout the peripheral edge 130. In this embodiment, the slots 122b are arranged approximately radially on the disk.

[0120] The slots 122b are arranged at equal intervals around the entire circumference of the peripheral edge 130. In this embodiment, the number of slots 122b is equal to the number of non-circular disk openings 122a. The slots 122b extend from the peripheral edge 130. The slots 122b extend toward the center of the flywheel disk 102.

[0121] Slot 122b has a width in the tangential direction of the flywheel disc 102. This width is narrower than the first width of the non-circular disc opening 122a.

[0122] While the slots and non-circular openings are substantially identical in this embodiment, this is not essential, and modifications are conceivable within the scope of the invention.

[0123] Each slot 122b intersects with the corresponding non-circular disk opening 122a. Each slot 122b is in contact with the central region or center point of each non-circular disk opening 122a.

[0124] Slot 122b provides a gap in the peripheral edge 130 of the flywheel disc 102. It will be understood that in other embodiments, gaps of other shapes may be provided. Various shapes of gaps will be apparent to those skilled in the art without departing from the scope of the present invention.

[0125] The nearly T-shaped non-circular disk opening 122a and slot 122b described above have been found to be particularly advantageous in reducing stress in the circular disk opening 120.

[0126] It will be understood that a given pair of non-circular openings 122a and slots 122b connected together can be considered to provide a non-circular opening. In this case, the larger non-circular opening can be considered to consist of a slot portion and a non-circular portion.

[0127] In other embodiments, it will be understood that the size of the disk openings may vary in relation to the size of the flywheel disk 102. For example, if a different number of disk openings are provided, the openings may be larger (for a smaller total number) or relatively smaller (for a larger total number) to accommodate a configuration comparable to the one in Figure 4.

[0128] In various embodiments, the flywheel disc 102 may have any integer number of various disc openings, the integer number of which is selected to be between 2 and 50 (including 2,50).

[0129] In other embodiments, it will be understood that any appropriate number of disk openings can be provided. Another embodiment of the flywheel disk is described below with reference to Figures 7 and 8.

[0130] Two of the threaded studs 114 are shown in more detail in Figure 5. Each threaded stud 114 can be thought of as a rod. Each threaded stud 114 extends through the corresponding circular disk opening 120 within the stack of disks 104. Each threaded stud 114 has a head 116 at the tip of the threaded stud. Similarly, a second head (not shown) may be provided at the other end of the stud 114. Each head 116 is threaded to receive a nut 126. The threaded studs 114 are used to clamp the plate member 106 to the outside of the stack 104, as described above.

[0131] Each threaded stud 114 has a neck portion 118. Each neck portion 118 can be considered a tapered neck or section with decreasing thickness.

[0132] In one embodiment, each neck portion may have a cross-section including opposing inwardly curved arcs. The inwardly curved arcs may be separated by the minimum width of the stud 114 at the midpoint of the neck portion.

[0133] Each neck portion 118 is positioned adjacent to its respective head 116. Each neck portion 118 is positioned adjacent to one of the multiple disks 102.

[0134] In this embodiment, each pair of heads 116 and neck portions 118 occupy an opening in the plate member 106, although it will be understood that in some less preferred embodiments, the heads may protrude from the plate member. Each neck portion 118 is fully received by the plate member 106 (but preferably not a stack of disks).

[0135] The length of the head 116 is equal to the length of the neck portion 118. Each neck portion 118 reduces the mass and bending stiffness of the stud 114. The neck portions 118 can reduce stress on the threaded stud 114, the plate member 106, and the disk 102 positioned adjacent to (particularly in direct contact with) the plate member 106.

[0136] Each head 116 in this embodiment has a hollow portion 124. The hollow portion 124 can be considered a recess in the head 116 of the threaded bolt 114. The hollow portion 124 reduces the mass of the threaded stud 114 and the load induced during the rotation of the flywheel.

[0137] The hollow portion and / or neck portion relieve pressure on the threaded stud when the flywheel 100 rotates.

[0138] Figure 6 shows a further embodiment of the flywheel 200, which is substantially the same as the flywheel 100 shown in Figure 5, with the following differences: In this embodiment, each disc is either a Laval-shaped disc or a rimmed Laval-shaped disc. That is, each disc has a thin portion (or thinner / thinner portion) 180 that extends somewhat inward from the region having circular and non-circular openings.

[0139] In this case, the thin portion 180 has an asymmetrical cross-section (for example, similar to an elongated teardrop shape) when viewed in a cross-section in the radially outward direction from the central longitudinal axis of the disk (i.e., the assumed axis of rotation) toward the periphery of the disk, but it will be understood that other cross-sectional shapes may be provided, and they may also be symmetrical.

[0140] The thin portion 180 is provided on both sides of the disk, i.e., the top and bottom surfaces. The thin portion 180 is a circular portion of the disk and extends in an annular manner in the circumferential direction of the disk. The Laval shape reduces stress at the center of the disk and allows for higher speeds at the expense of increased stress around the circular disk opening 120.

[0141] Figure 7 shows a further embodiment of the flywheel disc, which is generally shown as “202”. This embodiment is substantially similar to the disc described above, but has some differences, as will be explained here. In this embodiment, the ratio of circular disc openings 220 to non-circular disc openings 222a and slots 222b is 2:1. Two circular disc openings 220 are provided between the pair of non-circular openings 222a and slots 222b. This configuration can be thought of as an AAB type pattern, where A refers to the circular disc openings 220 and B refers to the non-circular disc openings 222.

[0142] Figure 8 shows a further embodiment of the flywheel disc, generally denoted as “302”. This embodiment is substantially similar to the disc described above. However, in this embodiment, the ratio of pairs of non-circular disc openings 322a and slots 322b to circular disc openings 320 is 2:1. Two pairs of non-circular openings 322a and slots 322b are provided between each circular disc opening 320. This configuration can be considered an ABB type pattern, where A refers to a circular disc opening 320 and B refers to a non-circular disc opening 322.

[0143] In some embodiments of the flywheel disc, an nA·mB type pattern may be provided, where n and m are positive integers. For example, when n is 2 and m is 3, the nA·mB type pattern is AABBB. In some embodiments, m and n have different values. In some embodiments, m and n have the same value. In embodiments where the non-circular opening 322a is not provided, m is 0.

[0144] In both embodiments shown in Figures 7 and 8, the openings 220, 222a and 320, 322a are arranged on a common pitch circle, but it will be understood that other embodiments of the flywheel disc may have some of the openings on other pitch circles or in a different arrangement that does not require the openings to be on a pitch circle.

[0145] The embodiments described above are provided merely as examples. Various changes and modifications will be apparent to those skilled in the art without departing from the scope of the invention as defined by the claims.

Claims

1. It is a flywheel, A plurality of disks arranged in a stack, the stack including at least first and second end disks at both ends, and each of the plurality of disks including a plurality of disk openings through which the disks pass, First and second plate members positioned at opposite ends of the stack, wherein one or both of the first and second plate members include a plurality of plate openings through which they pass for alignment with a corresponding series of disk openings passing through the stack, The system includes connecting means for clamping the first and second plate members together to the outside of the stack of disks, One, some, or each of the aforementioned multiple disk openings, A first set of circular disk openings for accommodating through the aforementioned connecting means, A second set of openings for reducing stress in or around the circular disk opening when the flywheel rotates, A flywheel wherein the second set of openings includes (i) a non-circular disk opening and (ii) a slot extending from the periphery of each of the disks, and each of the non-circular disk openings and / or the slots is positioned between a predetermined pair of the circular disk openings.

2. The flywheel according to claim 1, wherein the non-circular disc opening is substantially elliptical.

3. The flywheel according to claim 1 or 2, wherein each of the non-circular disk openings has a first width in the substantially tangential direction of the disk and a second width in the substantially radial direction of the disk, and the first width is greater than the second width.

4. The flywheel according to claim 3, wherein the first width of the non-circular disk opening is greater than the diameter of one predetermined circular disk opening.

5. The flywheel according to claim 3 or 4, wherein the second width of the non-circular disk opening is equivalent to the diameter of one predetermined circular disk opening.

6. The flywheel according to any one of claims 1 to 5, wherein the slot has a tangential width narrower than half the diameter of the circular disk opening.

7. The flywheel according to any one of claims 1 to 6, wherein the circular disk opening and the non-circular disk opening are arranged on a pitch circle.

8. The flywheel according to any one of claims 1 to 7, wherein in one, some, or all of the disks, the arrangement of the circular disk openings and the non-circular disk openings forms a repeating or alternating sequence with respect to at least a portion of the periphery of each disk.

9. The flywheel according to any one of claims 1 to 8, wherein the number of circular disk openings for accommodating the connecting means is equal to the number of non-circular disk openings or slots.

10. The circular disk openings are arranged at equal intervals along the peripheral edge of each disk. The slots are arranged at equal intervals along the peripheral edge of each disk. A flywheel according to any one of claims 1 to 9, wherein either or both of the above are provided.

11. A flywheel according to any one of claims 1 to 10, directly or indirectly referencing claim 3, wherein the non-circular disk openings are positioned away from the peripheral edge of each disk by a distance equivalent to the second width of at least one of the non-circular disk openings.

12. The flywheel according to claim 7, or the flywheel according to any one of claims 8 to 11 that references claim 7, wherein the number of circular disk openings on the pitch circle is greater than the number of non-circular disk openings on the pitch circle, or the flywheel according to claim 7, wherein the number of non-circular disk openings on the pitch circle is greater than the number of circular disk openings on the pitch circle.

13. The flywheel according to any one of claims 1 to 12, wherein at least one of the non-circular disk openings is connected to or intersects with at least one of the slots.

14. The flywheel according to any one of claims 1 to 13, wherein one or more pairs of the non-circular disk openings and the slots together provide one or more substantially T-shaped openings or open portions in one, some, or all of the disks.

15. The flywheel according to any one of claims 1 to 14, wherein one, some, or all of the connecting means are in contact with the side wall of the corresponding circular disk opening.

16. The flywheel according to any one of claims 1 to 15, wherein the diameter of each circular disk opening substantially coincides with the diameter of the cross-section of the connecting means.

17. The flywheel according to any one of claims 1 to 16, wherein the connecting means or each of the connecting means includes one or more hollow portions.

18. The flywheel according to any one of claims 1 to 17, wherein the connecting means includes one or more bolts or threaded studs.

19. The flywheel according to claim 18, wherein the threaded stud or each of the threaded studs includes a neck portion.

20. A flywheel disc for a flywheel, The flywheel disc includes a plurality of disc openings, The disk opening is, A first set of circular disk openings for accommodating through connecting means, A second set of openings for reducing stress in or around the circular disk opening when the flywheel rotates, A flywheel disc wherein the second set of openings includes (i) a non-circular disk opening positioned away from the periphery of each disk and (ii) a slot extending from the periphery of each disk, each of the non-circular disk openings and / or the slots positioned between a predetermined pair of circular disk openings.

21. It is a flywheel, A plurality of disks arranged in a stack, the stack including at least first and second end disks at both ends, each of the plurality of disks including a plurality of disk openings through which the disks pass, First and second plate members positioned at opposite ends of the stack, wherein one or both of the first and second plate members include a plurality of plate openings through which they pass for alignment with a corresponding series of disk openings passing through the stack, A flywheel comprising a plurality of rods for clamping the first and second plate members together to the outside of the stack of discs, each of which is of a certain length and is positioned through a corresponding series of the disc openings, and each of the rods having a first neck portion located in one of the corresponding plate openings of the first plate member.

22. The flywheel according to claim 21, wherein one, some, or all of the rods each have a second neck portion, the second neck portion being located in one of the corresponding plate openings of the second plate member, and the second neck portion being on the opposite side of the corresponding first neck portion of the rod.

23. The flywheel according to claim 21 or 22, wherein one, some, or all of the rods include at least one hollow portion.

24. The flywheel according to claim 23, wherein the at least one hollow portion is located at one or both of the first and second ends of each of the rods.

25. A flywheel assembly comprising one or more flywheels according to any one of claims 1 to 19 or 21 to 24, and / or one or more flywheel discs according to claim 20, A flywheel assembly wherein the flywheel or the flywheel disc is mounted to a drive assembly for propelling the rotation of the flywheel or the flywheel disc in order to store energy in at least one of the flywheel or the disc, or to extract energy from the flywheel or the disc.

Images