GREASE LUBRICATED TAPER ROLLER BEARING

Abstract: A taper roller bearing comprises at least one inner bearing ring and at least one outer bearing ring, each defining a tapered raceway, a series of taper rollers as well as a cage for spacing said rollers, said cage having two cage rings of different diameters which are interconnected by cage bars and defining cage pockets between each adjacent pair of cage bars, the cage ring having a relatively small diameter being positioned near the inner bearing ring raceway part with small diameter, and the other cage ring being positioned near the inner bearing ring raceway part with large diameter. The bearing is grease lubricated, and the cage bars have an essentially planar inner surface, on which a grease layer may adhere.

Description: Grease lubricated taper roller bearing The invention is related to a taper roller bearing, comprising at least one inner bearing ring and at least one outer bearing ring, each defining a tapered raceway, a roller set comprising a series of taper rollers as well as a cage for spacing said rollers, said cage having two cage rings of different diameters which are interconnected by cage bars and defining cage pockets between each adjacent pair of cage bars, the cage ring having a relatively small diameter being positioned near the inner ring part with small diameter or closely adjacent to the corresponding ring shoulder, and the other cage ring being positioned near the inner bearing ring part with large diameter or closely adjacent to the corresponding ring shoulders. Such taper roller bearings are widely known. As an example, the application of double row taper roller bearings in train axlebox bearing units is mentioned. Taper roller bearings are particularly fit for accommodation of combined loads (radial and axial). Bearing performance and durability largely depend on the lubrication of the bearing components, in particular the rollers, raceways and cages. In particular for long-term applications, and long service intervals, such as occur in the field of railway transport, a continuous and adequate supply of lubricant is decisive. In this respect, several problems are encountered in practice. High temperatures may develop in the bearing, which have a bad influence on the lubricating properties of the grease contained in the bearing. Also, peak temperature levels during initial running of the bearing may lead to problems. These problems are related to mechanical working of the grease, and to the amount of grease transported within the bearing during service. In particular, chunks of grease may suddenly come loose and migrate into the bearing, leading to further temperature increases as chunks are being worked. From US-A-4425011, a taper roller bearing is known having a cage designed for allowing better lubrication by means of an oil lubricant. However, this known bearing is not suitable for grease lubrication. The object of the invention is to provide a solution to these problems. This object is achieved in that the bearing is grease lubricated, and the cage bars have a planar inner surface on which a grease layer may adhere. During normal running, in service of the bearing, the grease migrates within the roller set and may then be thrown off. As a result of the centrifugal forces, the grease is driven somewhat along the cage bars, as new amounts of grease enter the region of the roller set. In general, an "equilibrium" layer is formed under each cage bar, which appears to be fairly constant for specific speeds and grease consistencies. This layer of grease is particularly fit for ensuring a proper lubrication of the bearing. The grease provides a lubrication effect by bleeding of the oil contained therein, which oil will directly reach the locations close-by, i.e. the rollers and corresponding cage bars. Transport of oil may take place through capillary action and in vapour state. According to a preferred embodiment, the inner surface of each cage bar runs obliquely from the small diameter cage ring to the large diameter cage ring, so as to promote grease lubricant migration towards the large diameter cage ring under the influence of centrifugal forces. The invention is related to different kinds of taper roller bearings; in particular however, the bearing may comprise two series of taper rollers, the roller of each series being spaced by a respective cage, the small diameter cage rings of said cage laying opposite each other and enclosing an intermediate space, wherein the intermediate space contains a grease lubricant. During service, the grease in the intermediate space may gradually migrate towards both rows of rollers. The grease may enter the rows of rollers through the gap between the inner ring or spacer ring and the small diameter cage ring. It may also enter through the gap between cage and outer ring. Subsequently, it reaches the roller ends and then the cage bars. According to a preferred embodiment therefore, the bearing may comprise two inner bearing rings separated by an intermediate bearing ring element, said bearing rings having each a raceway enclosed between a small diameter shoulder and a large diameter shoulder, wherein the small diameter cage ring surrounds the small diameter shoulder so as to promote grease lubricant migration from the intermediate space onto the cage bars. The small diameter cage ring may also surround at least part of intermediate ring for a similar purpose. The outer bearing ring may be a one piece outer bearing ring comprising two raceways. However, the outer bearing ring may comprise two separate adjacent bearing ring parts. The proximity of the cage rings to the shoulder also serves to stabilise the motion of the cage in service. The small diameter cage ring may project radially inwardly with respect to the inner surfaces of the cage bars; the large diameter cage ring may be flush with the inner surfaces of the cage bars. The small diameter cage ring may also project axially towards the intermediate space, beyond the end face of the inner bearing ring. The large diameter cage ring may also project radially inwardly with respect to the inner surface of the cage bars. In order to ensure a proper engagement of cage and rollers, each cage bar has two prongs facing away from the inner surface of said cage bar. Each prong may have an extension which extends over and is connected to the small diameter cage ring. In this way, a firm and stiff connection between prongs/cage bars and said ring is obtained. Furthermore, at least one sealing ring may be connected to the outer bearing ring. The invention will be described further with reference to the embodiment shown in the figures. Figure 1 shows a radial, partial section to a double taper roller bearing according to the invention. Figure 2 shows a cross-section according to II - II of a cage of the bearing according to figure 3. Figure 3 shows a cross section according to III - III according to figure 2. The taper roller bearing according to figure 1 comprises two inner bearing rings 1 and a single common outer bearing ring 2. The inner bearing rings 1 have tapered raceways 3, the outer bearing ring has tapered raceways 4. Two series of taper rollers 5 are in rolling contact with these raceways 3, 4. The inner bearing rings are mutually supported by means of an intermediate bearing ring element 6. By means of labyrinth seals 7, consisting of bearing ring parts 8, 9, the internal bearing space of the taper rolling bearing is closed. Each series of rolling elements 5 is spaced by means of cage 10. Said cage 10 has a cage ring 11 with a relatively small diameter, a cage ring 12 with a relatively large diameter, and a number of cage bars 13 connecting these cage rings 11, 12. Between adjacent cage bars 13, cage pockets 14 are defined for accommodating a taper roller 5. Each cage bar 13 has two prongs 15, for holding the taper rollers 5 within the corresponding cage pocket 14. The cage ring 11 with small diameter surrounds the small diameter shoulder 16 of the inner ring 1 closely. Large diameter cage ring 12 surrounds large diameter shoulder 17 of inner ring 1 as well. Said cage ring 11 has some overhang above the intermediate ring element or central spacer 6. This overhang provides controlled entrainment of grease to feed the roller set with lubricant. According to the invention, an amount of grease 18 is applied in the internal bearing space between outer bearing ring 2, intermediate bearing ring element 6 and both cages 10. Also, an amount of grease 19 is applied to the cages 10. In service of the bearing, grease 18 may migrate from the internal bearing space through the gap defined between the small diameter cage ring 11 and the small diameter shoulder 16 towards the underside 20 of cage bar 13. The grease may also migrate between the small diameter cage ring 11 and the outer bearing ring 2. Subsequently, grease may migrate further through the gap defined by large diameter cage ring 12 and large diameter shoulder 17, as indicated by arrow 22. The grease 19 may adhere permanently to the underside 20 of cage bar 13, thereby providing a suitable lubrication of the taper rollers 5. The oil may bleed from the grease directly on the running surfaces of the bearing. The prongs 15 are extended by means of extensions 23, which provide a rigid connection between the cage bars 13 and the small diameter cage ring 11. The extensions 23 are chamfered so as to reduce the mechanical influence on the migration of grease, and hence moderate the temperature increases otherwise due to working of the grease. Moreover, the shape of the extensions 23 facing the central space permits the volume of grease 18 to remain in place without excessive mechanical disturbance. This permits the grease volume to remain close to raceway region 3, facilitating migration of lubricant to said raceways. It also provides a larger unswept volume enabling a larger reservoir for grease fill in said central space.

Claims: Claims 1. Taper roller bearing, comprising at least one inner bearing ring (1) and at least one outer bearing ring (2), each defining a tapered raceway (3, 4), a series of taper rollers (5) as well as a cage (10) for spacing said rollers (5), said cage (10) having two cage rings (11, 12) of different diameters which are interconnected by cage bars (13) and defining cage pockets (14) between each adjacent pair of cage bars (13), the cage ring (11) having a relatively small diameter being positioned near the inner bearing ring raceway part with small diameter, and the other cage ring (12) being positioned near the inner bearing ring raceway part with large diameter, characterized in that the bearing is grease lubricated, and the cage bars (13) have an essentially planar inner surface (20), on which a grease layer may adhere (19). 2. Bearing according to claim 1, wherein the inner surface (20) of each cage bar (13) runs obliquely from the small diameter cage ring ( 11 ) to the large diameter cage ring (12), so as to promote grease lubricant migration towards the large diameter cage ring (12) under the influence of centrifugal forces. 3. Bearing according to claim 1 or 2, wherein the inner surfaces of the cage bars (13) coincide with an imaginary cone surface which is coaxial to the cage. 4. Bearing according to claim 1, 2 or 3, comprising two series of taper rollers (5), the rollers of each series being spaced by a respective cage (10), the small diameter cage rings (11) of said cages (10) lying opposite each other and enclosing an intermediate space, wherein the intermediate space contains a grease lubricant (18). 5. Bearing according to claim 4, comprising two inner bearing rings (1) separated by an intermediate ring element (6), said bearing rings (1) having each a raceway (3) enclosed between a small diameter shoulder (16) and a large diameter shoulder (17), wherein the small diameter cage ring (11) surrounds the small diameter shoulder (16) so as to promote grease lubricant migration from the intermediate space onto the cage bars (13). 6. Bearing according to claim 4 or 5, wherein the outer bearing ring (2) is a one piece outer bearing ring comprising two raceways (4). 7. Bearing according to claim 4 or 5, wherein the outer bearing ring comprises two separate outer bearing ring parts. 8. Bearing according to any of the preceding claims, wherein the small diameter cage ring (11) projects radially inwardly with respect to the inner surfaces (20) of the cage bars (13). 9. Bearing according to any of the preceding claims, wherein the large diameter cage ring (12) projects radially inwardly with respect to the inner surfaces (20) of the cage bars (13). 10. Bearing according to any of the preceding claims 1-7, wherein the small diameter cage ring (11) is flush with the inner surfaces (20) of the cage bars (13). 11. Bearing according to any of the preceding claims 1-7, wherein the large diameter cage ring (12) is flush with the inner surfaces (20) of the cage bars (13). 12. Bearing according to any of the preceding claims, wherein each cage bar (13) each has two prongs (15) facing away from the inner surface (20) of said cage bar (13). 13. Bearing according to any of the preceding claims, wherein at least one sealing ring (7, 8) is connected to the outer bearing ring (2), grease (21) being applied in the gap defined by each sealing ring (7, 8) and the large diameter cage ring (12). 14. Bearing according to any of the preceding claims, wherein the cage bars (13) each have an extension (23) which extends over the small diameter cage ring (11). 15. Bearing according to claim 14, wherein each extension (23) is chamfered towards the axially outer end of the small diameter cage ring (11). 16. Bearing according to claim 14 or 15, wherein each cage bar (13) has two prongs (15), each prong (15) being extended by an extension (23). 17. Bearing according to any of the preceding claims, wherein the cage ring (11) with relatively small diameter is positioned closely to the small diameter shoulder (16) bordering the inner bearing ring raceway part with small diameter. 18. Bearing according to any of the preceding claims, wherein the cage ring (12) with relatively large diameter is positioned closely to the large diameter shoulder (17) bordering the inner bearing ring raceway part with large diameter.

Inventors: MARTINETTI MAURIZIO, PERSSON MATS JOHAN, SKILLER JOHN VINCENT, MARTINETTI, MAURIZIO, PERSSON, MATS, JOHAN, SKILLER, JOHN, VINCENT
Applicants: MARTINETTI MAURIZIO, PERSSON MATS JOHAN, SKF ENG & RES CENTRE BV, SKILLER JOHN VINCENT, MARTINETTI, MAURIZIO, PERSSON, MATS, JOHAN, SKF ENGINEERING & RESEARCH CENTRE B.V., SKILLER, JOHN, VINCENT
Application year: 1999
Main classification: F16C33
IPC codes: F16C19, F16C33