ROLLING ELEMENT BEARING HAVING A COOLING CAGE

Abstract: A rolling element bearing comprises an outer ring (1) and an inner ring (2) each with a raceway, said rings enclosing a series of rolling elements (3) which are in rolling contact with the raceways, and a cage (4) having cage bars (8) between which pockets are defined for accommodating a rolling element (3) each. The cage (4) has cooling means (7) for preventing grease or lubricant leaving the cage as a result of an increase in temperature.

Description: Rolling element bearing having a cooling cage The invention is related to a rolling element bearing comprising an outer ring and an inner ring each with a raceway, said rings enclosing a series of rolling elements which are in rolling contact with the raceways, and a cage having cage bars between which pockets are defined for accommodating a rolling element each. Such rolling element bearings, for instance a spherical roller bearing, are widely known. Rolling element bearing are generally provided with a lubricant such as a grease. During service, the oil bleeds from the grease and is finally depleted. Thus, after a certain service period, the bearing should be relubricated. The maximum time allowable between relubrication of the bearing constitutes an important property. In particular, for spherical roller bearings, the maximum time interval for relubrication appears to be too small. Said interval does not only depend on the running conditions of the bearing and the bearing design, but also on the amount of grease which can be maintained in place on the cage bars, that is close to the surface of the rolling elements. In this respect, it appears that the temperature for the cage is determinant for the amount of grease which can be retained, and also for the bleeding rate of the grease. As a consequence, this temperature is decisive for the length of the time period during which a proper lubrication of the bearing can be maintained. As an example, a doubling of this time period is obtained for every 10 - 15 °C temperature drop of the cage. In service, the cage of a spherical roller bearing may reach an overtemperature of 30 - 70 °C. Such relative high temperature thus shortens the maximum lubrication time interval appreciably. The object of the invention is therefore to provide a bearing which has a better lubrication time interval. This object is achieved in that the cage has cooling means for preventing grease or lubricant leaving the cage as a result of an increase in temperature. In particular, the cooling means are for cooling the cage bar. The cooling means prevent the temperature of the cage to rise in service, whereby the cage bars are able to hold the grease in a proper position for lubricating the rolling elements. The cooling means may have areas of the cage having enlarged surfaces, which enlarged surfaces are bounding the bearing space, or are outside the bearing space. Such surfaces can be cooled by the outside atmosphere of the bearing, in particular during rotation of the cage. Preferably, the cage has cooling elements having an external cooling surface facing towards the outside of the bearing space. According to a first possibility, the cooling elements fit between the outer ring and inner ring. However, according to a second possibility, the cooling elements overlap one of the rings on the outside. In case the cooling elements are perforated, an increased cooling effect may be obtained as a result of the turbulent flow thus generated. The cooling elements may comprise a ring or disc fastened on the cage or a ring or disc which is integrally formed with the cage. The invention will further be described with reference to the embodiments shown in the figures. Figure 1 shows a radial cross-section through a first embodiment of the bearing according to the invention. Figure 2 shows a cross-section through a second embodiment. Figure 3 shows a sideview of the bearing according to figure 1. Figure 4 shows a sideview of the bearing according to figure 2. Figure 5 shows a further embodiment. The bearing shown in figure 1 has an outer ring 1, an inner ring 2, and a series of balls 3. The series of balls 3 is contained in a cage 4. Said cage has cage pockets 5, onto which extensions 6 are connected each carrying a cooling element 7 or a (continuous) cooling disc. The cage pockets are each defined between a pair of cage bars 8. Thus, the cooling elements 7 have the cooling effect on the cage bars 8. The grease which collects on the cage bars 8, is thereby cooled as well, thus providing a better retaining capability for the grease on the cage bars 8. A controlled release of the lubricant contained in the grease is now ensured for longer periods, leading to longer lubrication interval times. The embodiment of figure 2 shows a roller bearing having an outer race 9, an inner race 10, rollers 11 and a cage 12. The cage 12 has cage pockets 13, defined between a pair of cage bars 14 each. Cage bars 14 are directly connected to cooling elements 15, whereby also a cooling effect for the cage bars 14 is ensured. Figure 5 shows an embodiment wherein a ring 16 is connected to the cage (not visible). This configuration has the advantage that more grease can be held in the vicinity of the rolling elements resulting in improved lubrication.

Claims: Claims 1. Rolling element bearing, comprising an outer ring (1, 9) and an inner ring (2, 10) each with a raceway, said rings enclosing a series of rolling elements (3, 11) which are in rolling contact with the raceways, and a cage (4, 12) having at least one cage ring and cage bars (8, 14), between which cage bars (8, 14) pockets (5, 13) are defined for accommodating a rolling element (3, 11) each, characterized in that the cage has cooling means (7, 15) for preventing an increase in temperature. 2. Rolling element bearing according to claim 1, wherein the cooling means are for preventing an increase in temperature of a grease or lubricant. 3. Rolling element bearing according to claim 1 or 2, wherein the cooling means (4, 12) are for cooling at least one cage bar (8, 14). 4. Rolling element bearing according to any of the preceding claims, wherein the cooling means (7, 15) comprise areas of the cage (4, 12) having enlarged surfaces which enlarged surfaces are bounding the bearing space. 5. Rolling element bearing according to according to any of the preceding claims, wherein the cooling means (7, 15) comprise areas of the cage (4, 12) having enlarged surfaces which enlarged surfaces are outside the bearing space. 6. Rolling element bearing according to any of the preceding claims, wherein the cage (4, 12) has cooling elements (7, 15) having an external cooling surface facing towards the outside of the bearing space. 7. Rolling element bearing according to claim 6, wherein the cooling elements (7) fit between the outer ring (1) and inner ring (2). 8. Rolling element bearing according to claim 6 or 7, wherein the cooling elements (15) overlap one of the rings (9) on the outside. 9. Rolling element bearing according to any of claims 6-8, wherein the cooling elements act as shields which at last partly close off the bearing space defined between the rings (1, 2, 9, 10). 10. Rolling element bearing according to any of claims 6-9, wherein the cooling elements (7, 15) are perforated for creating a turbulent cooling flow. 11. Rolling element bearing according to any of the preceding claims, wherein the cooling elements comprise a ring or disc fastened on the cage. 12. Rolling element bearing according to any of the preceding claims wherein the cooling elements comprise a ring or disc which is integrally formed with the cage. 13. Rolling element bearing according to any of the preceding claims, wherein the cooling means (7, 15) extend radially inside and/or outside with respect to a cage ring. 14. Rolling element bearing according to any of the preceding claims, wherein the cooling means (7, 15) extend axially outside with respect to a cage ring. 15. In a rolling element bearing, comprising an outer ring (1, 9) and an inner ring (2, 10) each with a raceway, said rings enclosing a series of rolling elements (3, 11) which are in rolling contact with the raceways, and a cage (4, 12) having at least one cage ring and cage bars (8, 14), between which cage bars (8, 14) pockets (5, 13) are defined for accommodating a rolling element (3, 11) each, use of cooling means for cooling the cage so as to prevent grease or lubricant leaving the cage as a result of an increase of temperature during service of said bearing.

Inventors: IOANNIDES EUSTATIOS, JACOBSON BO OLOV, IOANNIDES, EUSTATIOS, JACOBSON, BO, OLOV
Applicants: IOANNIDES EUSTATIOS, JACOBSON BO OLOV, SKF ENG & RES CENTRE BV, IOANNIDES, EUSTATIOS, JACOBSON, BO, OLOV, SKF ENGINEERING & RESEARCH CENTRE B.V.
Application year: 1999
Main classification: F16C33
IPC codes: F16C33, F16C37