ROLLER BEARINGS

Abstract

A roller bearing comprises inner and outer rings defining a toroidal inner raceway rotatable about a bearing axis (A). A plurality of concave rolling elements is arranged in a single row between the outer and inner rings. Each of the plurality of concave rolling elements is a symmetrical cylindrical roller having circular ends, a roller axis passing through the centre of the circular ends, and a concave side profile that extends continuously between the circular ends. The toroidal inner and outer raceways each have a convex race surface that continuously engages the concave side profile between the circular ends of each concave rolling element with a first radius and extends axially beyond the circular ends of each concave rolling element with a second radius that is less than the first radius.

Claims

1. A roller bearing comprising: an inner ring defining a toroidal inner raceway rotatable about a bearing axis; an outer ring defining a toroidal outer raceway rotatable about the bearing axis; and a plurality of concave rolling elements arranged in a single row between the outer and inner rings; wherein each of the plurality of concave rolling elements is a symmetrical cylindrical roller having circular ends, a roller axis passing through the centre of the circular ends, and a concave side profile that extends continuously between the circular ends, the roller axis being aligned with the bearing axis; and wherein the toroidal inner and outer raceways each have a convex race surface that continuously engages the concave side profile between the circular ends of each concave rolling element with a first radius and extends axially beyond the circular ends of each concave rolling element with a second radius that is less than the first radius.

2. The roller bearing of claim 1, wherein each concave rolling element comprises: a main portion wherein the concave side profile has a radius R that increases from a centre line of the single row of concave rolling elements towards the circular ends having a diameter 2r; and an end portion wherein the concave side profile has a radius R that decreases until R=r.

3. The roller bearing of claim 1, comprising a cage ring comprising a plurality of cages to house the concave rolling elements between the outer and inner rings.

4. The roller bearing of claim 3, wherein each cage follows the concave side profile of the concave rolling elements and has a thickness (z) defined circumferentially along the single row of concave rolling elements.

5. The roller bearing of claim 4, wherein the single row of concave rolling elements has a centre line passing circumferentially between the outer and inner rings, and the cage thickness (z) is a maximum at the centre line.

6. The roller bearing of claim 3, wherein the cage ring is made from steel.

7. The roller bearing of claim 3, wherein the cages are impregnated or coated with a solid lubricant.

8. The roller bearing of claim 1, wherein the concave rolling elements make full contact with the race surfaces all the way along the concave side profile between the circular ends.

9. A method of assembling the roller bearing of claim 1, the method comprising: assembling some of the plurality of concave rolling elements inside the outer ring to form an incomplete single row of concave rolling elements defining a circumferential gap; arranging the axis of the inner ring substantially perpendicular to the axis of the outer ring and aligning the inner ring with the circumferential gap; positioning the inner ring inside the outer ring with the axis of the inner ring aligned with a diameter of the outer ring; assembling a remainder of the plurality of concave rolling elements in the circumferential gap inside the outer ring to form a complete single row of concave rolling elements; and rotating the inner ring into the plane of the outer ring and aligning the axis of the inner ring with the axis of the outer ring.

10. The method of claim 9, wherein the circumferential gap is at least as wide as the inner ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures, in which:

[0023] FIG. 1a is a schematic half sectional view of a spherical roller bearing according to the prior art;

[0024] FIG. 1b is a schematic partial top view on arrow X of FIG. 1a;

[0025] FIG. 2a is a schematic half sectional view of a roller bearing according to an example of the present disclosure;

[0026] FIG. 2b is a schematic partial top view on arrow Y of FIG. 2a of the concave rolling elements and cage ring inside the roller bearing of FIG. 2a;

[0027] FIG. 2c is a schematic side view of a concave rolling element; and

[0028] FIGS. 3a-3d schematically illustrate an exemplary method of assembly for a roller bearing according to an example of the present disclosure.

DETAILED DESCRIPTION

[0029] FIGS. 1a and 1b show a single row of spherical rollers 1 in the form of a cylindrical roller having a convex side profile. A roller bearing comprises an inner ring 2 and outer ring 3 having radial contact with the spherical rollers 1. A cage ring 4 includes cages that enclose each roller 1, the cages having a thickness z between adjacent rollers 1. FIG. 1b shows two adjacent rollers 1 and part of a cage ring 4 (note the inner and outer rings have been omitted for clarity). A roller bearing e.g. CARB having this construction is self-aligning and used mainly for radial loads.

[0030] FIG. 2a shows a roller bearing comprising an inner ring 20 defining a toroidal inner raceway rotatable about a bearing axis A and an outer ring 30 defining a toroidal outer raceway rotatable about the bearing axis A. The toroidal raceways are seen in FIG. 3. A plurality of concave rolling elements 10 is arranged in a single row between the outer and inner rings 20, 30. It can be seen that each of the plurality of concave rolling elements 10 is a symmetrical cylindrical roller having a concave side profile 12, hereinafter referred to as a concave roller. The concave roller 10 is aligned with the bearing axis A. It can also be seen that the outer and inner rings 20, 30 each have a convex race surface 20a, 30a that continuously engages the concave side profile 12 of the concave rollers 10 with a first radius, the convex race surface 20a, 30a extending axially beyond the ends of the rollers 10 with a second radius that is less than the first radius. This enables axial displacement to be accommodated.

[0031] FIG. 2c shows the concave side profile 12 of a concave roller 10 that extends continuously between its circular ends 14. The roller axis A passes through the centre of the circular ends 14. The circular ends 14 have the same diameter 2r. It may be seen that, in a main portion 16 of the roller 10, the concave side profile 12 has a radius R that is a minimum at the centre line CL of the single row of rollers 10 and increases towards the circular ends 14. In the end portions 18, the concave side profile 12 has a maximum end radius R1 that decreases until R=r at the circular ends 14. The end portions 18 therefore provide a smooth transition between the concave side profile 12 and the circular ends 14. As the roller 10 is symmetrical, both end portions 18 have the same end radius R1.

[0032] FIGS. 2a and 2b show a cage ring 40 forming cages between the concave rollers 10. It can be seen from FIG. 2b that each cage in the ring 40 follows the concave side profile 12 of the concave rollers 10 and has a thickness Z defined circumferentially along the single row of concave rollers 10. The single row of concave rollers 10 has a centre line CL passing circumferentially between the outer and inner rings, and the cage thickness Z is a maximum at the centre line CL. By comparing FIGS. 1b and 2b, it can be seen that the cage thickness Z between the concave rollers 10 is greater than in conventional spherical roller bearings, for example up to 15% greater.

[0033] FIGS. 3a to 3d illustrate how the concave rollers 10 can be assembled with the inner and outer rings 20, 30 that define a toroidal raceway. As is clearly seen already in FIG. 2a, the toroidal inner and outer raceways each have a convex race surface for engaging the concave rollers 10. In FIG. 3a, two of the cages in the ring 40 are left empty when the concave rollers 10 are assembled inside the outer ring 30. In FIG. 3b, the inner ring 20 is placed inside the outer ring 30, perpendicular to its plane of orientation. In FIG. 3c, the two missing rollers 10 are added to the empty cages in the cage ring 40. In FIG. 3d, the inner ring 20 is rotated into the plane of the outer ring 30 to complete the final roller bearing assembly. In this final step, the inner ring 20 is rotated to get all planes of the bearing components such as inner ring 20, outer ring 30, and bearing cage ring 40, together parallel to each other.