RAILWAY VEHICLE WHEEL WITH IMPROVED DAMPING CHARACTERISTICS

Abstract: A railway vehicle wheel comprises a hub (2) and a tire (3) carrying a flange (6), which hub and tire are mutually connected by means of a disc (13) or a number of spokes. The tire (3) comprises a thin visco-elastic layer (8) for dissipating vibrations originating from the contact of the railway vehicle wheel with a railway track. Said visco-elastic layer (8) is circular and concentric to the tire (3).

Description: 1 Railway vehicle wheel with improved damping characteristics The invention is related to a railway vehicle wheel comprising a hub and a tire provided with a flange, which hub and tire are mutually connected by means of a disc or a number of spokes. In operation, the contacts between rails and railway constitute sources of vibrations which are transmitted to the wheel shaft. Consequently, these vibrations are also imposed on the bearings and finally the superstructure of a train wagon or locomotive. They are experienced by the passengers and train personnel as unpleasant; moreover, fatigue of the steel material of the wheels and shafts may be aggravated thereby. From US-A-5183306, a railway vehicle wheel is known comprising a rubber ring situated between the hub and the tire of the wheel. In a radial cross-section, said ring has an U-shape, leading to radial shear of the rubber material. The ring has a large thickness, of the same order of magnitude as the tire. A disadvantage of this known railway vehicle wheel is its rather great radial resilience, and the complicated structure with separate connecting rings and bolts. The object of the invention is to provide a railway vehicle wheel having improved damping properties, while maintaining its stiffness. This object is achieved in that the tire comprises a thin visco-elastic layer for dissipating vibrations originating from the contact with a railway track. In the rail wheel according to the invention, visco-elastic material layer is applied that dissipates energy under shear. In particular, vibration energy is thereby damped out quickly despite the small thickness of the layer. Said thickness is of a smaller order of magnitude than the thickness of the tire. According to the invention, the visco-elastic layer is loaded under shear in the circumferential (or tangential) direction, which provides the required relative displacements in the rubber layer for obtaining the desired damping properties. Preferably, the visco-elastic layer is circular and concentric to the tire. Thus, the layer is of a simple and straightforward design, which enables a relatively cheap and easy manufacturing process of the wheel in question. To optimize the damping, the visco-elastic layer is situated at a distance from the depth at which maximum shear occurs in the tire, said shear resulting from the contact between the tire and the railway track under rolling motion of the wheel on the track. The position to be selected depends on the load on the wheel, which defines the shear stress at each depth, and the fatigue strength of the visco-elastic material. Said depth is selected as a compromise between the useful life of the layer, and the amount of energy dissipation required. Said dissipation and fatigue are governed by the shear stresses experienced by the visco-elastic layer. Thus, the damping can be adjusted in dependence of the field of application, as a compromise between life and vibration reduction. In particular, the distance of the visco-elastic layer to the rolling surface of the tire may be smaller than the depth at which maximum shear occurs in the tire. A reliable construction is obtained in case the tire comprises a main ring body carrying the flange, as well as a concentric ring body, the visco-elastic layer being interposed between the main ring body and the concentric ring body. Said concentric ring body at the side facing away from the flange is held against coming off from the main ring body by a fixing means. In case the visco- elastic layer would be damaged, the integrity of the railway vehicle wheel in question is still guaranteed so as to provide the required safety in service. The fixing means may be a fixing ring mounted on the main ring body. Said fixing ring may be mounted onto the main ring body by means of an interference fit. Other mounting means could be applied as well, such as bolts or adhesives. Moreover, at least two layers of visco-elastic material are applied, said layers being each surrounded by a concentric ring body. The thickness of the visco-elastic layer is of a smaller order of magnitude than the thickness of the tire. Moreover, at least two layers of visco-elastic material can be applied. The invention will be described further with reference to an example of a railway vehicle wheel according to the invention as shown in the figures. Figure 1 shows a radial cross-section view of the railway vehicle wheel according to the invention. Figure 2 shows an axial view of a part of the wheel according to figure 1. . The railway vehicle wheel 1 as shown in figure 1 comprises a hub 2 and a tire 3 which are interconnected by means of connecting disc 13. The tire 3 has an inwardly protruding rim 4, which together with a clamping ring 5 provides the required connection between said tire 3 and the connecting disc 13. The tire 3 carries a flange 6, for guidance of the railway vehicle wheel with respect to the rail 7. According to the invention, the tire 3 has a thin layer 8 of a visco-elastic material, at a distance from its rolling surface 9. In the embodiment shown, the visco-elastic layer 8 is covered by means of a steel ring 10, which rests with its one sideface to the facing surface 11 of flange 6. The steel ring 10 and the main ring body 15 of the tire 3 are firmly held together by means of a fixing ring 14. Said fixing ring 15 is mounted by means of an interference fit on the main ring body 15, in such a way that the visco-elastic layer 8 as well as the steel ring 10 are held captive between said fixing ring 14 and the flange 6. In the axial view of figure 2, wherein the fixing ring 14 has been omitted for reasons of clarity, a part of the railway vehicle wheel has been depicted, together with a part of the railway track 7. Also a schematic representation 12 of the shear stress distribution in the thickness of the wheel, starting from its rolling surface 9, has been given. At the depth dl, the shear stress is at a maximum, but the visco- elastic layer 8 is situated at a distance d2. At position d2, the shear stresses are somewhat lower, and thereby the damping effect, resulting from the deformations of the visco-elastic layer 8 due to the shear stresses, is somewhat less. On the other hand, the visco-elastic material 8 is exposed to less heavy shear loads, which is beneficial for a longer service life. Thus, the depth d2 at which the layer of visco-elastic material 8 is situated, has been selected as a compromise between optimized damping and fatigue life.

Claims: 4 Claims 1. Railway vehicle wheel (1), comprising a hub (2) and a tire (3) provided with a flange (6), which hub (2) and tire (3) are mutually connected by means of a disc (13) or a number of spokes, characterized in that the tire (3) comprises a thin visco-elastic layer (8) for dissipating vibrations originating from the contact of the railway vehicle wheel (1) with a railway track (7). 2. Railway vehicle wheel according to claim 1, wherein the visco-elastic layer (8) is circular and concentric to the tire (3). 3. Railway vehicle wheel according to claim 1 or 2, wherein the visco-elastic layer (8) is situated at a distance from the depth at which maximum shear occurs in the tire, said shear resulting from the contact between the tire (3) and the railway track (7) under rolling motion of the wheel (1) on the track (7). 4. Railway vehicle wheel according to claim 3, wherein the distance of the visco-elastic layer (8) to the rolling surface (9) of the tire is smaller than the depth at which maximum shear occurs in the tire (3). 5. Railway vehicle wheel according to claim 3 or 4, wherein the distance of the visco-elastic layer (8) to the rolling surface (9) of the tire (3) is selected dependent on the wheel load. 6. Railway vehicle wheel according to claim 3, 4 or 5, wherein the distance of the visco-elastic layer (8) to the rolling surface (9) of the tire (3) is selected dependent on the fatigue strength of the visco-elastic material. 7. Railway vehicle wheel according to any of the preceding claims, wherein the tire (3) comprises a main ring body (15) carrying the flange (6), as well as a concentric ring body (10), the visco-elastic layer being interposed between the main ring body (15) and the concentric ring body (10). 8. Railway vehicle wheel according to claim 7, wherein the concentric ring body (10) at the side facing away from the flange (6) is held against coming off from the main ring body (15) by a fixing means (14). 9. Railway vehicle wheel according to claim 8, wherein the fixing means is a fixing ring (14) mounted on the main ring body (15). 10. Railway vehicle wheel according to claim 9, wherein the fixing ring (14) is mounted onto the main ring body (14) by means of an interference fit. 11. Railway vehicle wheel according to any of the preceding claims, wherein at least two layers of visco-elastic material are applied, said layers being each surrounded by a concentric ring body. 12. Railway vehicle wheel according to any of the preceding claims, wherein the thickness of the visco-elastic layer (8) is of a smaller order of magnitude than the thickness of the tire (3).

Inventors: IOANNIDES EUSTATHIOS, WITTMEYER HENNING HANS, IOANNIDES, EUSTATHIOS, WITTMEYER, HENNING, HANS
Applicants: IOANNIDES EUSTATHIOS, SKF ENG & RES CENTRE BV, WITTMEYER HENNING HANS, IOANNIDES, EUSTATHIOS, SKF ENGINEERING & RESEARCH CENTRE B.V., WITTMEYER, HENNING, HANS
Application year: 1999
Main classification: B60B17
IPC codes: B60B17