A FLY WHEEL ARRANGEMENT

Abstract: A fly wheel arrangement comprising a rotatable axle (1), a ring (4) essentially forming the rotating mass of the fly wheel and a connecting means (5) made from fibre-reinforced connecting the ring (4) with the axle (1) or with a part rotating herewith. The connecting means (5) is connected to the ring (4) at its outer end portion and to the axle (1) or a part connected hereto at its inner end portion. The connecting means (5) has essentially the shape of a cylinder or a conical shell.

Description: Title : A Fly Wheel Arrangement Field of Invention The invention relates to a fly wheel arrangement comprising a rotatable axle, a ring essentially forming the rotating mass of the fly wheel and a connecting means made from fibre-reinforced plastics connecting the ring with the axle or with a part rotating herewith, the connecting means being glued to the ring at its outer end portion and to the axle or a part connected hereto at its inner end portion. Background Art DK-B-160.687 discloses a fly wheel of the above type, wherein the connecting means has a plate-like, cross-sectional low U shape. The known fly wheel arran¬ gement comprises two or four such connecting means grouped in pairs, each being glued to the ring and a hub wedged on the axle at their inner and outer end portions, respectively. During rotation of the fly wheel the ring generates strong centrifugal forces, and if the fly wheel is placed in moving transport means, such as airplanes or vehicles, the fly wheel arrangement is also subjected to a strong gyroscopic torque. The above mentioned forcesin particular make heavy demands on the inner glued joints between the connecting means and the hub. The expan¬ sion of the ring produced by the centrifugal forces results in large angular displa¬ cements in the connecting means and as a result hereof corresponding high stresses. As indicated above these stresses in particular may cause problems at the inner glued joints with the hub. Disclosure of Invention The object of the invention is to provide a fly wheel arrangement of the above type, wherein the stresses in the connecting means and in particular in the con- nection between the latter and the axle is reduced in relation to prior art. The fly wheel arrangement according to the invention is characterised in that the connecting means has the shape of a cylinder or a conical shell, whereby the gyroscopic forces or other acceleration forces acting on the fly wheel arrangement may be transferred essentially as tension or compressive forces in the connecting means without causing bending moments. According to the invention, the connecting means may comprise fibres following an essentially circumferential path and fibres following a longitudinal path essen¬ tially at right angles to the circumferential fibres. The longitudinal fibres are able to absorb the tension and compression caused by from the gyroscope torque, and the connecting means may comprise several circumferential fibre layers of varied thickness, fibre content and fibre material, whereby the density and the E-module thereof may be varied in the circumferential direction in such a manner so as to give a desired smooth deflection curve for the longitudinal generatrix. The expansion of a freely rotating ring is determined by the ratio between the density and the E-module, and the connecting means may be considered as composed of a plurality of such rings. Furthermore, according to the invention the inner glued joint between the axle and the connecting means may be arranged at a diameter at least three times the bearing diameter of the axle, i.e. the smallest diameter of the axle. As a gyro- scopic torque at any point causes forces in the joint which are inversely propor¬ tional to the square of the distance of the point from the axis of rotation, the joint may advantageously be placed as far away from the axis of rotation as possible. Moreover, according to the invention the axle may comprise a radially projecting disc ending at its outer periphery in an annular body projecting axially at least in one direction. The inner end of the connecting means is glued to the lower face of said annular body. This embodiment is particularly advantageous, as the centri¬ fugal force thus causes pressure to arise in the glued joint. A proper glued joint may be subjected to approximately the same shear stress in its entire joint area. The annular body on the disc is usually more rigid than the connecting means to be glued herewith. Consequently, the stress in the glue joint increases with the distance from the disc. However, by another embodiment of the invention this may be compensated for by arranging a plastics dies of a cross- sectional wedge shape, and increasing height in the direction away from the annular body, on the lower face of the annular body between the latter and the connecting means. This plastics material or matrix material preferably having a low or no fibre content, has a lower shear modulus than the two elements between which it is arranged. Consequently, the plastics material ensures that the same shear stress is obtained in the entire glued joint. Brief Description of the Drawings The invention is explained in detail below with reference to the drawings, in which Fig. 1 is an axial, sectional view through a first embodiment of a fly wheel arrangement according to the invention and Fig. 2 is an axial, sectional view through an alternative embodiment of the fly wheel arrangement according to the invention. Best Mode for carrying out the invention The preferred embodiment of the fly wheel arrangement shown in Fig. 1 compri¬ ses a rotatable axle (1) of steel with an integrally shaped, projecting disc (2) ending an annular body (3) projecting axially and having a cross-sectional triangu¬ lar shape. Further, the fly wheel arrangement comprises an annular ring (4) made from fibre-reinforced plastics, preferably from a carbon fibre-reinforced plastics, said annular ring being connected to the annular body (3) on the projecting disc (2) of the rotatable axle (1) by means of a connecting means (5). The connecting means (5) has the shape of a conical shell body and comprises an inner plastics layer (6), in which the fibres are arranged in the longitudinal direc¬ tion, and an outer layer (7), in which the fibres extend circumferentially essential- ly at right angles to the longitudinal fibres in the inner plastics layer (6). The inner plastics layer (6) extends further than the outer plastics layer and is glued to a bevelling (9) in the ring (4) at its outer end (8) by means of an outer glued joint (10). At its inner end (11) the connecting means (5) is glued to a wedge- shaped plastics disc (13) by means of a first inner glued joint (12), said plastics disc being glued to the lower face (15) of the ring body (3) on the projecting disc (2) of the axle (1) by means of a second inner glued joint (14). The inner plastics layer (6) comprising longitudinal fibres as well as the outer plastics layer (7) comprising circumferential fibres of the connecting means (5) are dimensioned and arranged in such a manner that during rotation the connect- ing means (5) deflects in accordance with a smooth deflection curve without too small radii of curvature and resulting unacceptable stresses, when the ring (7) expands due to the centrifugal forces. By arranging the cross-sectionally wedge- shaped plastics ring (13) between the inner end (11) of the connecting means and the lower face of the annular body (3) an even distribution of the shear stresses is ensured in the glued joints (12, 14). The inner glued joints are arranged at a diameter substantially larger than the smallest diameter of the axle or the bearing diameter in order to reduce the stresses in the glued joints. The alternative embodiment of fly wheel arrangement according to the invention shown in Fig. 2 comprises an axle (21) consisting of two identical axle halfs (22) each having a conically diverging end portion (23) adjacent to their axle ends. At (38) each of the end portions (23) are welded to a corresponding leg of the con¬ necting ring (36) being essentially V-shaped in a cross-sectional view. The axle halfs and the connecting ring are preferably made from aluminium. The fly wheel arrangement further comprises a ring (24) essentially forming the rotating mass of the fly wheel and having an inner radial projection (37) adjacent to one end, and a connecting means (25) connecting the ring (24) to the axle (21). The connecting means (25) is a cylindrical body of fibre-reinforced plastics and shaped in such a manner that the desired deflection curve is formed with appropri¬ ately large radii of curvature. The outer end portion (28) of the connecting means (25) is glued to the inner surface (29) of the inner radial projection (37) of the ring (24) by means of a outer glued joint (30). The inner end portion (31) of the cylindrical connecting means (25) engages a groove (35) formed in the connecting ring (36) and is glued to the groove (35) by means of an inner glued joint (32). The matrix or basic material in the fibre-reinforced plastics may comprise a plurality of plastics materials, such as polyester, epoxy and PES. Likewise, various different fibres may be used for the fibre-reinforcement, such as glass or carbon fibres depending on the desired strength and bending properties of the connecting means.

Claims: Claims 1. A fly wheel arrangement comprising a rotatable axle (1 ,21), a ring (4,24) essentially forming the rotating mass of the fly wheel and a connecting means (5, 25) made from fibre-reinforced plastics connecting the ring (4,24) with the axle (1, 21) or with a part rotating herewith, the connecting means being glued to the ring (5, 25) at its outer end portion and to the axle (1,21) or a part connected her¬ eto at its inner end portion, characterised in that the connecting means (5,25) essentially has the shape of a cylinder or a conical shell. 2. An arrangement as claimed in claim 1, characterised in that the connecting means (5,25) comprises fibres (7) following an essentially circumfe¬ rential course as well as fibres (6) following an essentially longitudinal course at essentially right angles to the circumferential course. 3. An arrangement as claimed in claim 1, characterised in that the inner glued joint (12,14,35) between the axle (1,21) and the connecting means (5,25) is arranged at a diameter at least three time the bearing diameter of the axle. 4. An arrangement according to one or more of the preceeding claims, characterisedin that the axle comprises a radially projecting disc (2) ending at its outer periphery in an annular body (3) projecting axially at least in one direction, and that the inner end (11) of the connecting means (5) is glued to the lower face (15) of said annular body (3). 5. An arrangement according to claim 4, characterised in that a plastics disc (13) of a cross-sectional wedge shape and increasing height in the di¬ rection away from the annular body (3) is arranged on the lower face of the annular body (3) between the latter and the connecting means (5).

Inventors: WAAGEPETERSEN GASTON BIRGER FO, WAAGEPETERSEN, GASTON, BIRGER, FOG
Applicants: RISOE FORSKNINGSCENTER, WAAGEPETERSEN GASTON BIRGER FO, FORSKNINGSCENTER RISOE
Application year: 1993
Main classification: F16F15
IPC codes: F16C15, F16F1, F16F15