Technical field

The present disclosure relates to improved lubrication of a bearings. Specifically, the present disclosure relates to a new bearing cage design and a bearing provided with such a cage.

Background

Bearings comprising an inner ring, an outer ring, a plurality of rolling elements, such as rollers or balls, distributed between the inner ring and the outer ring often use a cage positioned between the inner ring and the outer ring for separation and/or guiding of the rolling elements. Some bearings are provided with axial seals configured to seal between the inner ring and the outer ring. The seals are provided on opposite axial sides of the cage such that the cage and the rolling elements are confined in a space, wherein the space is delimited by the seals, the inner ring and the outer ring. A problem with such bearings is that their friction increases over time. Another problem with such bearings is that the seals wear out.

Summary

An object of the present invention is to mitigate increase of friction in the bearing and to mitigate premature wear of the bearing seals.

According to a first aspect of the present disclosure, these and other objects are achieved by a bearing cage as defined in claim 1 , with various embodiments described in dependent claim 2. The cage comprises a side wall portion extending circumferentially about a central axis of the cage. The side wall portion comprises a central opening aligned with the central axis. The cage comprises a circumferential cage bar extending from a radially outer portion of the side wall portion. The cage bar is configured to keep rolling elements, such as balls or rollers, of the bearing separated. The side wall portion comprises a plurality of recesses extending radially outwards about the central axis from the central opening. Thus, instead of having a circular central opening, the present disclosure teaches the provision of the above mentioned recesses. The recesses enable movement of lubricant between opposite axial sides of the side wall portion of the cage, i.e. between a side facing the rolling elements, and a side facing the respective seal. At relative rotation between the outer ring and the inner ring as a bearing provided with such a cage is used, lubricant moves around in the space inside the bearing due to centrifugal force and due to stickiness of lubricant to moving surfaces. The movement of lubricant is subjected to a centrifugal force acting radially outwards on the lubricant. Although centrifugal force tends to move lubricant radially outwards away from the inner ring, reducing the amount of lubricant present closer to the inner ring, at the same time, lubricant moves through the recesses in the cage from the side facing the rolling elements to the side facing the seal or vice versa. Accordingly, the proposed cage design enables improved lubrication closer to the inner ring and by the seal, thus mitigating increased friction and mitigating wear of the seal.

The recesses may be evenly distributed about the circumference of a radially inner portion of the side wall portion. The even distribution of the recesses keep the cage axially balanced and promotes an even distribution of lubricant around the inner ring by the seal.

According to a second aspect of the present disclosure, these and other objects are also achieved by a bearing as defined in claim 3, with various embodiments described in dependent claims 3-8. The bearing comprises an inner ring, an outer ring, and a plurality of rolling elements distributed between the inner ring and the outer ring. The bearing further comprises the above described cage positioned between the inner ring and the outer ring such that the cage bar separates the rolling elements. Also, the bearing comprises two axial seals configured to seal between the inner ring and the outer ring. The seals are provided on opposite axial sides of the cage such that the cage and the rolling elements are confined in a space, said space being delimited by the seals, the inner ring and the outer ring. Further, a lubricant is provided in the space for lubrication.

Upon rotation of the inner ring relatively the outer ring, the rolling elements keep the inner ring aligned inside the outer ring whilst enabling low friction between the inner ring and the outer ring. The cage keeps the rolling elements separated from each other and correctly positioned within the bearing. The seals protect the bearing from contamination, and also keeps the lubricant confined inside the bearing. The lubricant lubricates surfaces inside the bearing to reduce friction and wear. As mentioned above, the recesses enable movement of lubricant between opposite axial sides of the side wall portion of the cage, i.e. between a side facing the rolling elements, and the side facing the respective seal. Although centrifugal force tends to move lubricant radially outwards away from the inner ring, reducing the amount of lubricant present closer to the inner ring, at the same time, lubricant moves through the recesses in the cage from the side facing the rolling elements to the side facing the seal or vice versa. The seals keep the lubricant within the inner space of the bearing. Accordingly, the proposed cage design enables improved lubrication closer to the inner ring and by the seal, thus mitigating increased friction and mitigating wear of the seal.

The outer ring may comprise at least one refill opening for introduction of lubricant into the space. The refill opening(s) may be used to inject lubricant before seals are installed at assembly of the bearing, and the refill opening(s) may also be used to introduce lubricant after the seals have been installed. If more than one refill opening are provided, lubricant may leave the inner space of the bearing through one refill opening as lubricant is injected through another refill opening, to allow introduction of more lubricant with reduced risk of displacement of the seals caused by pressure increase in the bearing. Alternatively, the size of the refill opening may be large enough to allow gas to leave through the same refill opening as the one through which lubricant is injected into the bearing.

The central opening of the side wall portion may be sized to fit with the inner ring such that the cage 1 rotates in the same rotational direction as the inner ring when the bearing is in use.

Each seal may comprise a sealing lip at the radially inner circumference of the respective seal for sealing to the inner ring. Each sealing lip is spaced apart from the cage enough to allow movement of lubricant through the recess even at axial relative displacement of each cage with respect to each respective adjacent sealing lip at axial loading of the bearing, preferably with a spacing when the bearing is axially loaded of at least 0.1 mm.

The bearing may be a radial bearing or a thrust bearing.

Brief description of drawings

Fig. 1 shows a perspective view of a bearing according to a first embodiment of the present disclosure.

Fig. 2 shows a cross sectional view in section A of the bearing also shown in fig. 1. Figs. 3-5 show various views of a cage for use in the bearing shown in figs. 1-2.

Detailed description

A first embodiment of a cage 1 for a bearing 2 will hereinafter be described with reference to the appended drawings in conjunction with the use of the cage 1 in a first embodiment of a bearing 2.

As shown in figs. 1-5, the cage 1 is positioned inside a bearing 2 for keeping rolling elements 7 of the bearing 2 separated and correctly positioned within the bearing 2. In this embodiment, the rolling elements 7 are rollers, but in other embodiments, the rolling elements 7 may be balls, or a combination thereof. As shown in fig. 2, the illustrated bearing 2 comprises two cages - one cage 1 for each row of rolling elements 7 of the bearing 2. In other bearing designs, a single cage 1 may be sufficient, for example when the bearing 2 only has one row of rolling elements 7. The cage 1 comprises a side wall portion 3 extending circumferentially about a central axis 4 of the cage 1. The side wall portion 3 comprises a central opening 5 aligned with the central axis 4. The central opening 5 of the side wall portion 3 is sized to fit with the inner ring 9 such that the cage 1 rotates in the same rotational direction as the inner ring 9 when the bearing 2 is in use.

The cage 1 further comprises a circumferential cage bar 6 extending from a radially outer portion of the side wall portion 3. The cage bar 6 is provided with recesses or openings for each rolling element 7 and the material between the recesses/openings positions and guides the rolling elements 7 within the bearing 2.

The side wall portion 3 comprises a plurality of recesses 8 extending radially outwards about the central axis 4 from the central opening 5.

The recesses 8 enable improved movement of lubricant between opposite axial sides of the side wall portion 3 of the cage 1 , i.e. between a side facing the rolling elements 7, and a side facing a respective seal 11 of the bearing, as shown in fig. 2.

At relative rotation between the outer ring 10 and the inner ring 9 as a bearing provided with such a cage 1 is used, lubricant moves around in the space inside the bearing due to centrifugal force and due to stickiness of lubricant to moving surfaces. As shown by the arrows in fig. 2, movement of lubricant is subjected to a centrifugal force acting radially outwards on the lubricant. Although centrifugal force tends to move lubricant radially outwards away from the inner ring 9, reducing the amount of lubricant present closer to the inner ring 9, at the same time, lubricant moves through the recesses in the cage 1 from the side facing the rolling elements 7 to the side facing the seal 11 or vice versa. Accordingly, the proposed cage 1 design enables improved lubrication by the inner ring 9 and by the seal 11 , thus mitigating increased friction and mitigating wear of the seal 11.

The recesses 8 are evenly distributed about the circumference of a radially inner portion of the side wall portion 3. The even distribution of the recesses 8 keep the cage 1 axially balanced and promotes an even distribution of lubricant around the inner ring 9 by the seal 11. In other embodiments, the circumferential distribution and sizing of the recesses 8 may alternatively be different, i.e. not evenly distributed recesses of a same size and shape.

The two axial seals 11 are configured to seal between the inner ring 9 and the outer ring 10. The seals 11 are provided on opposite axial sides of the cage 1 such that the cage 1 and the rolling elements 7 are confined in a space, said space being delimited by the seals 11, the inner ring 9 and the outer ring 10. Further, a lubricant is provided in the space for lubrication.

Each seal 11 comprise a sealing lip at the radially inner circumference of the respective seal 11 for sealing to the inner ring 9. Each sealing lip is spaced apart from the cage 1 enough to allow movement of lubricant through the recess even at axial relative displacement of each cage 1 with respect to each respective adjacent sealing lip at axial loading of the bearing 2, preferably with a spacing when the bearing 2 is axially loaded of at least 0.1 mm.

Upon rotation of the inner ring 9 relatively the outer ring 10, the rolling elements 7 keep the inner ring 9 aligned inside the outer ring 10 whilst enabling low friction between the inner ring 9 and the outer ring 10. The seals 11 protect the bearing 2 from contamination and oxidation, and also keeps the lubricant confined inside the bearing.

The outer ring 10 comprises three refill openings 12 for introduction of lubricant into the space. The refill openings 12 may be closed by plugs (not illustrated) which can be temporarily removed for access to the refill openings 12. In other embodiments, any suitable number of refill openings 12 may alternatively be provided instead, or the refill openings may be omitted.

The refill opening 12 enables injection of lubricant after seals 11 have been installed at assembly of the bearing 2. If more than one refill opening 12 are provided, lubricant may leave the inner space of the bearing 2 through one refill opening 12 as lubricant is injected through another refill opening 12, to allow introduction of more lubricant with reduced risk of displacement of the seals 11 caused by pressure increase in the bearing 2. Alternatively, the size of the refill opening 12 may be large enough to allow gas to leave through the same refill opening 12 as the one through which lubricant is injected into the bearing 2.

Although a specific bearing 2 design and cage 1 design is illustrated and described herein, it should be understood that the present disclosure is not limited to this specific design and that the same principles are applicable to many other bearing designs, such as a cylindrical roller bearing, a tapered roller bearing, a ball bearing, a toroidal roller bearing. For example, the cage bar of the cage 1 is adapted to the design of rolling elements 7 of choice of the bearing 1. The lubricant may for example be oil or grease.