FR2574499A1 - Flywheel with rim supported by flexible straps - Google Patents

Abstract

The flywheel which can be supported inside a housing connected to a suction source so that surface friction is reduced consists of a ring (32) connected by flexible straps (22) to the driving shaft (28). The straps are formed by an endless cable wound several times around the ring, which is pear-shaped in cross-section, and also around two spherical bosses (24,26) one each side of the ring, mounted on the driving shaft. The loops are alternately expanded and contracted. To assist the stretching action, the two bosses can slide axially along the shaft within a certain distance, acting against springs on the shaft, between the bosses, the turns winding and unwinding around the ring and bosses. The ring has a core (58) of e.g. lead, carrying an outer ballast layer (56) of e.g. fibres, all enclosed by a flexible outer layer (62).

Description

Steering wheel device for storing
kinetic energy.

 The present invention relates to flywheel devices used to store kinetic energy and it relates, more particularly, to flywheels made of a filamentary material.

 Flywheels have been used to store energy for a number of years. Their use for this purpose was, however, limited, largely for cost reasons. The costs associated with this type of energy storage are slowly decreasing due to the use of advanced materials and designs; but considerable progress still needs to be made before the storage by means of frills becomes commercially viable.

 The amount of energy stored in a flywheel depends on the mass of the flywheel rotor and the square of the speed at which the mass rotates. As the speed increases with the distance to the axis of rotation, the energy stored in a given mass increases with its distance from the axis of rotation. Consequently, for any given speed of rotation, the most effective is to concentrate the mass of the rotor at the greatest possible distance from the axis of rotation. to maximize the stored energy.

For this reason, flywheel rotors have been proposed in which the outer rims of relatively heavy rotors are connected to a central hub by relatively light spokes (or spokes).

 The size of the steering wheels is, however, generally limited by considerations of space. To store the same amount of energy as a large flywheel, a small flywheel must rotate at a higher speed, which causes greater forces in the flywheel rotor. Consequently, the amount of energy that can be stored in a flywheel is limited by the ability of the flywheel structure to withstand the considerable forces exerted in a mass rotating rapidly around an axis.

 A rotating flywheel rotor applies a resulting force to the axis around which it rotates. This resulting force depends on the moment of inertia of the rotor and its angular speed. Because any moving mass tends to move in a straight line, rather than in a circle centered on an axis, the mass of the rotor would tend to move in a straight line, without the antagonistic centripetal force transmitted through the spokes. to the rim and in the strength of the structure of the rim itself. The centripetal force keeps the rim of the steering wheel on the hub. Since the result of the flywheel rotor depends on the speed of rotation and the mass of the rotor, a greater centripetal force is required to maintain the cohesion of the rotor, when the speed of rotation of the rotor or its mass is increased.

 During acceleration and deceleration of the flywheel, additional forces are generated in a flywheel rotor. These forces, which are due to the relative inertia and force of the rim and the hub, can cause the spokes of the flywheel to jump, which are already under stress from the centripetal force.

 The inability of steering wheel structures to withstand the physical stresses generated by these forces has limited the size, speed and use of the steering wheels. In an attempt to solve this problem, flywheels have recently been designed using filamentary materials for certain parts of the flywheel, to take advantage of their high tensile strength, compared to amorphous or crystalline materials of high density such as l cast steel.

Glass, aramid and carbon fibers and steel wires represent some of the filamentary materials considered for flywheel structures. These low density materials, which have a high resistance / mass ratio, make it possible to increase the speed of the flywheels, while reducing their risk of disintegration due to the tensions generated by the rotation. However, these materials are unable to withstand significant transverse stresses. Due to this limitation, among others, the flywheel structures made of these materials have not been completely successful and have not exhibited sufficient service lives at high speeds.

 There is therefore a need for a flywheel device made of a filamentary material capable of withstanding the tensions generated at high rotational speeds.

 Consequently, the subject of the invention is a flywheel energy storage device comprising a rim made of wound fiber filaments and spokes made of flexible fiber filaments.

 The invention also relates to a flywheel energy storage device of this type, imposing pure compression forces on the hub, which allows high speeds of rotation.

 This flywheel allows very high rotational speeds, with no probability of breakage due to the fatigue of the material by the use of monofilament fibers for the rim and spokes, and the arrangement of the fibers so as to subject them to tensile forces and to minimize shear forces.

 The spokes made of fiber filaments are attached to a two-piece hub. The hub halves are each fixed to a central shaft so as to rotate at the same time as it around an axis, but they are allowed to move axially along the shaft between predetermined stops. Preferably, the hub halves are initially positioned by springs, outside the plane perpendicular to the shaft, defined by the rim.

 To reduce the tensions applied to the spokes of the steering wheel during acceleration, deceleration and high-speed rotation, the hub halves move closer together by sliding, in reaction to the rotational tensions transmitted via the spokes, to effectively lengthen the spokes and directly reduce their tensions.

The hub and rim tensions are reduced indirectly by the general reduction of the transmitted tensions of which the structure is the seat, which result therefrom.

 In a preferred embodiment, the flywheel energy storage device also comprises a housing enclosure. This housing enclosure is primarily used to contain flywheel debris and to dissipate the energy of the stored flywheel, in the event of failure of the flywheel rotor. For this purpose, the housing enclosure comprises a deflector screen and a material charged with water.

 During the disintegration of a flywheel rotor, the deflector screen forces the flywheel rotor to come into contact with the water-laden material. The friction of the rotating flywheel causes the water contained in the water-laden material to pass into the vapor state. The rotational energy of the flywheel is thus absorbed efficiently by conversion into thermal energy.

 Another characteristic of the preferred embodiment of the invention consists in using the shaft of the flywheel rotor as a pumping device to empty the flywheel housing, and thus reduce the friction of the air on the flywheel rotor. . Consequently, during the rotation of the flywheel, air is supplied through the shaft from the inside of the housing enclosure to the outside environment, which empties the chamber.

Other characteristics, objects and advantages of the invention will emerge from the following detailed description of a preferred non-limiting embodiment thereof, with reference to the appended drawings in which:
Figure 1 is a side view, partially broken away, of a flywheel rotor rim and a housing enclosure
Figure 2 is a perspective view of the flywheel rotor of Figure 1;
Figure 3 is a sectional view of the rim and hub of the flywheel rotor of Figure 2
Figure 4 is a plan view of the rim of the flywheel rotor of Figure 2 where the hub, shaft and all spokes except a small part have been removed
Figure 5 is an enlarged view of a section of the rim and the hub of the steering wheel;
Figure 6 is a sectional view of a steering wheel hub
Figure 7 is an axonometric view of a flywheel shaft, with partial cutaway
Figure 8 is a cross section of the flywheel shaft of Figure 7, taken along line 8-8; and
FIG. 9 is an axonometric view of a variant of the flywheel shaft shown in FIGS. 7 and 8.

 FIG. 1 shows a flywheel energy storage device 10, in which a flywheel housing 20 contains a flywheel rotor 30. The rotor 30 is connected; by means of a shaft 28, both to a source of rotation energy and to an energy exploitation device, such as an electric motor (not shown) and a generator (not shown, The electric motor is used to turn the flywheel, when the system is connected to an external energy source. The momentum of the flywheel is thus used to store energy.

When the stored energy is needed, the generator converts the stored energy into electrical energy.

 Energy is stored in the flywheel rotor, which includes a rotor rim 32, spokes or spokes 22 and hubs 24, 26. The rim 32 is connected to the hubs 24 and 26 by the spokes 22. The hubs 24, 26 of the rotor are mounted on a shaft 28 so as to rotate at the same time as it, but they can slide axially along the shaft between preset positions. During the rotation of the steering wheel, the hubs-24 and 26 are free to move towards each other to effectively lengthen the spokes 22 and reduce their tensions due to the acceleration, deceleration and the centripetal force generated by the rotation of the rotor of the steering wheel.

The lengthening of the spokes also prevents the spokes from applying destructive transverse stresses to the rim, at their fixing points. This increases the energy storage capacity and the duration of use of the steering wheel device 10.

 The rotor rim and its method of attachment to the hubs 24 and 26 are more particularly indicated in FIGS. 2 to 5.

 The rim 32 consists mainly of monofilament fibers 56. The fibers are wound in a circular shape from a single fiber or a bundle and they can be wound in any desired cross section. The fibers are oriented circumferentially inside the rim, to take advantage of the high tensile strength of the material. This orientation makes the best use of the resistance of the fibrous material, because the strongest stresses which appear in the rim during rotation are oriented in a similar manner.

 The rim 32 has an ovoid cross section, the obtuse end being at the outer periphery of the rim. The inner section 58 of the rim may be made of a material heavier than the fibers, to increase the total mass of the rim and thus increase its capacity for storing energy. The interior section 58, or ballast, is therefore made of lead or other dense metal. The weight of the ballast must be carefully adjusted, however, so as not to cause excessive tension on the fibers constituting the largest part of the rim, during operation of the rotor.

 The inner periphery of the rim has inwardly directed cavities 60 (FIG. 4) which are used for dynamic balancing of the rim of the steering wheel, before final assembly. Dynamic balancing is carried out by the selective insertion of weights into the cavities 60.

 The rim is covered in its entirety by an elastic skin 62 fitted tightly. This skin is made up of an elastic material of relatively high tensile strength, such as silicone rubber, which contributes to maintaining the cohesion of the fibers of the rim and constitutes a relatively soft interface between the rim and the spokes. The same high tensile strength material is also interposed between the ballast and the fibrous portion of the rim, to form a smooth elastic surface 63 therebetween. The soft interfaces formed between the rim elements minimize the transverse forces exerted on the fiber filaments at these interfaces.

 Each of the spokes 22 wraps around the rim 32 of the rotor and partially surrounds a half of the hub 24, 26, before returning to the rim. The spokes alternate between the lower half of the hub 26 and the upper half of the hub 24, axially centering the rim at equal distance between the halves 24, 26 of the hub.

A single fiber filament is used to surround each of the spokes, and this greatly increases the resistance of the spokes, eliminating the need to bind the filaments. The number of spokes can vary depending on the resistance required, determined by the diameter of the rim and the maximum speed of the steering wheel.

 The fibers which form the spokes 22 are oriented, along their longitudinal axes, towards the center of rotation of the flywheel, so as to coincide with the direction of the centripetal forces exerted by the spokes. Grooves 72, Figure 5, formed on the hubs of the steering wheel, constitute seats for spokes. The grooves are arranged, and their variable depth calculated, so as to prevent physical contact of the spokes, which would cause unwanted transverse pressure exerted on the fibers, at the locations of crossing of the spokes.

 Because the spokes are made of a flexible material, some relative angular displacement is possible between the rim and the hubs during acceleration and deceleration. This allows the spokes to insert or slightly disengage from the grooves of the hub during the periods of acceleration and deceleration. The ability to fit into and out of the hub decreases the deformation of the spokes in response to the differential rotation of the rim and the halves of the hub.

 The hub is shown in detail in Figure 6. Although each hub half 24, 26 can slide along the longitudinal axis of the central shaft 28, the hub halves are positioned on the shaft 28 by a section keying 78 of the hub and a keying section 79 of the shaft, so that there can be no relative rotational movement between these halves and the shaft.

The hub halves 24 and 26 are suspended elastically in mutual opposition and, at rest, they are positioned outside the plane defined by the rotor 30 of the flywheel and perpendicular to the shaft 28. Each of the identical hubs has an internal cavity 64 containing a spring spacer 70 and two springs 66 and 68. These springs react against the rear wall 65 of the cavity and a nut 84 of the shaft, to apply a force which separates the hubs from the plane of the rim of the flywheel .

 When the flywheel rotor accelerates or decelerates, slight differences in rotational speed are produced between the rim and the hubs, due to the inertia of the rim. This slight relative rotation of the rim and the hub would cause very high tensions in the spokes, without the action due to the split hub. The hubs are driven by the spokes towards the nut 84 in reaction to the differential rotation of the hub and the rim. This movement of the hubs acts as a shock absorber and gives the spokes a more effective length by reducing the angle between the spokes and the plane of the rim. The movement of the hub thus reduces the stress of the spokes which could otherwise lengthen the spokes beyond their shear limit and thus reduce the life expectancy of the flywheel. Any relative rotation between the hubs and the rim is thus compensated by the flexibility spokes and by the axial displacement of the hubs.

 It should be noted that the rims of the steering wheel tend to get larger at high rotational speeds and that, therefore, the spokes of this device are also effectively lengthened when the diameter of the rim increases, to prevent separation from the rim.

When the spokes are pulled outward by the enlargement of the rim, the hubs come together, lengthening the spokes and reducing the tensions of the spokes. The elastic force generated by the compression of the springs 66 and 68 brings the hubs back to their initial position when the flywheel stops turning.

 Preferably, light materials are used to make the hubs, in order to reduce the weight of the flywheel in the central portion of the relatively inefficient engine (for storing energy). The reason why the hubs can be made with security in a relatively light material, such as aluminum, is that the only forces transmitted by the spokes to the hubs of this device are compression forces, not tension. Consequently, the design of the hub attachment and spokes avoids relying on a hub structure limited by the tensile or shear strength of the hub material.

 The shaft 28 of the flywheel is made in two parts 80 and 82 which are held together by the nut 84 of the shaft and a male end 85. The evacuation of the housing chamber 20, FIG. 1, allows the flywheel to operate relatively free from air friction. this; which reduces the dynamic friction exerted on the steering wheel (or drag). To maintain a low air pressure in the chamber 20, the shaft 28 of the flywheel rotor is protected against air leakage by pressure seals 34 and 36, which may be magnetic, FIG. 1, at its junction with the housing enclosure.

 Figures 7 and 8 show two ways in which the shaft can be shaped to evacuate the air from the housing enclosure, which avoids having to use an external vacuum pump. The shaft comprises an internal structural element 86 and an external sheath 88. An air intake excavation 90 is formed in the external sheath 88 on a portion of the shaft inside the housing enclosure. Air enters the shaft cavity through the air intake 90 and is accelerated outside of an air outlet 92 by an air path 94 formed on the interior member 86. The air outlet 92 is placed on a portion of the shaft outside the housing enclosure.

 The helical air path 94 has a cross section whose area gradually decreases from its maximum section at the opening of the air intake 90 to its smallest section at the outlet 92 of the air path. This decreasing section causes the air to compress as it approaches the outlet of the air path, so that the air pressure at the outlet is higher than the surrounding air pressure. Therefore, the air is expelled from the shaft at the outlet 92, while the air pressure at the inlet 90 is reduced so that air is evacuated from the housing enclosure. The air outlet 92 may also include an automatic air valve (not shown) to prevent air from returning from the outlet orifice inside the enclosure, when the rotation of the flywheel slows down. an increase in air pumping is required, it is possible to provide two or more helical air paths in parallel along the length of the shaft, from multiple air intakes to multiple air outlets.

 According to a variant of the invention, shown in Figure 9, a plurality of ventilation fins 95 inclined so as to act as ventilation blades, are located inside a hollow shaft 100, near an outlet 109. An air passage 103 is formed between the fins and an air intake 105 placed inside the enclosure 20 for housing the steering wheel. The fins rotate while the shaft rotates and expels air from the housing enclosure.

 The flywheel housing also provides a safety device to retain flywheel debris and dissipate flywheel energy, if the flywheel decays during rotation. The failure of the steering wheels is, in general, due to the fatigue of the rim structure and spokes, due to an intense operating cycle, or to the progressive plastic enlargement of the rim. Consequently, the steering wheel housing enclosure 20 is shaped so as to deflect a steering wheel rim which disintegrates towards a material loaded with water. For this purpose, the structure 38 of the housing enclosure, FIG. I, and a deflector ring 48 adjacent to the plane of the rotor 32, are constituted by a hard material, such as steel. The interior surface 50 of the deflector ring 48 has ribs or convolutions, or has another abrasive texture, so that when the rim 32 expands or is no longer concentric, it touches the deflector ring and begins to undergo abrasion. Because of this abrasion, the rim deforms into a soft plastic shapeless mass of fibers, which is projected along the deflector ring, without necessarily fragmenting. This is desirable because it prevents the formation of hard fragments which behave like dangerous projectiles. Such fragments, and the risks which result therefrom, are shared with the rupture of the flywheels whose rim is made up of a cast material, such as steel, or even by a mass of fibers linked by an agent such as an epoxy material. The structure 38 of the housing enclosure and the deflector ring 48 tend, in combination, to bring down a rim which disintegrates in a protective screen 52 charged with water.

 The protective screen 52 loaded with water has a honeycomb structure (cellular structure) which retains a large amount of water. The screen loaded with water 52 can be constituted by a semi-solid gel or a polyester soaked in water. Polyesters soaked in water have a consistency similar to that of plaster, but they contain up to 75% water that is not chemically bound. The water coming from the protective screen is released when it is pierced by the steering wheel rim 32 which disintegrates. The friction produced by the interaction of the disintegrating flywheel and the housing enclosure and the protective screen transforms the rotational energy of the flywheel into heat, which increases the temperature of the water and causes it to pass to the water. 'state of vapor. The transformation of water into vapor absorbs considerable energy and therefore dissipates the stored rotational energy of the flywheel rotor which disintegrates, while preventing the material constituting the flywheel from igniting during the disintegration.

 The vapor produced by the water-filled protective material tends to fill the housing and build up pressure which further slows down the rotor. As the interior pressure of the enclosure continues to increase, a relief valve 54 opens and allows vapor to escape into the atmosphere without danger. If necessary, steam can be removed from the flywheel via pipes.

 It goes without saying that many modifications of details can be made to the preceding description and to the appended drawing without thereby departing from the invention.

Claims (14)

 1. -A flywheel device for the storage of kinetic energy, characterized in that it comprises a rotor (30) comprising a shaft (28) which can rotate about an axis, a hub (24, 26) in several clamps placed on the shaft (28) so as to rotate at the same time as it and spokes or spokes (22) in fiber filaments wound around the hub and a rim (32), so that the spokes of filaments hold the rim concentric with respect to the shaft and the rim generally defines a plane perpendicular to this axis, in that the multi-piece hub comprises an element placed on each side of said pan and capable of sliding axially along the shaft to lengthen the spokes appropriately during the rotation of the flywheel to reduce the tensions generated in the spokes.  2. Steering wheel according to claim l, characterized in that the rim further comprises an elastic envelope (62) to maintain the integrity of its structure and constitute a soft interface between the rim and the spokes.  3. Steering wheel according to claim 1, characterized in that the spokes can surround and be partially released from the elements of the hub during acceleration and deceleration of the steering wheel.  4. Steering wheel according to claim 1, characterized in that the spokes alternate sequentially between the elements of the hub.  5. Steering wheel according to claim 1, characterized in that the rim further comprises a ballast (58).  6. Steering wheel according to claim 5, characterized in that the ballast is placed near the inner periphery of the rim.  7. Steering wheel according to claim 1, characterized in that it further comprises an enclosure (38) for housing said steering wheel, said enclosure comprising a material charged with water (52) to absorb the energy of the steering wheel during its disintegration.  8. Steering wheel according to claim 7, characterized in that the housing enclosure has an abrasive surface.  9. Steering wheel according to claim 7, characterized in that the shaft further comprises air pumping means (51) to evacuate the enclosure during the rotation of the steering wheel.  10. Steering wheel according to claim 1, characterized in that the elements of the hub further comprise grooves which constitute housings for spokes.  11. Steering wheel according to claim 10, characterized in that the grooves have different depths to reduce the shear stresses.  12. Steering wheel according to claim 1, characterized in that springs tend to move the elements of the hub away from said plane.  13. Steering wheel according to claim 1, characterized in that the rim is made of fiber.  14. Steering wheel according to claim 5, characterized in that the ballast comprises means for receiving balancing weights.