GB2166811A - Tapered roller bearing - Google Patents

Abstract

A roller bearing comprising inner and outer raceways with tapered rollers 14 therebetween and a retaining ring 13 mounted in a groove 16 adjacent the large ends of the rollers. The retaining ring has an annular lip which acts to retain the rollers during assembly of the bearing, and a flange which extends radially inwardly to define, with adjacent parts, a reservoir for lubricant. <IMAGE>

Description

SPECIFICATION Improvements relating to tapered roller bearings This invention relates to tapered roller bearings, particularly of the type for use in the pilot position in gearboxes for automotive vehicles.

Figure 1 of the accompanying drawings is a transverse section through a typical gearbox arrangement in which the pilot bearing is coaxially located between the input shaft and the output shaft.

The illustrated gearbox comprises an input shaft 1, coaxial output shaft 2 and parallel layshaft 3. The input and output shafts are rotatably mounted in respective roller bearings 4 and 5 and are rotatably mounted with respect to one another by means of a pilot bearing 6 mounted within a cavity 10 formed in the end of the input shaft. Drive from the input shaft to the layshaft is transmitted by means of constant mesh gears 7 and 8. Drive from the layshaft to the output shaft is transmitted by way of a selected one of a number of synchromesh coupling arrangements 9.

When the gearbox is engaged in one of the low-speed ratios, the drive is transmitted from the constant-mesh gear 7 on the input shaft to the constant-mesh gear 8 on the layshaft and then through the selected one of the pairs of output gears to the output shaft. In these circumstances, the output shaft rotates at a lower speed than the input shaft and the pilot bearing 6 accommodates this relative rotation while supporting forces transmitted between shafts 1 and 2 resulting from gear loads.

It is customary in such gearboxes to use single helical gears in all positions to achieve quiet and smooth operation. It is also customary to arrange the design so that the axial forces, induced in the input and output shafts by driving forces transmitted through the helical gears, are directed away from the pilot bearing and are supported by the other bearings 4 and 5 on these two shafts. This means that a bearing of comparatively small size may be used in the pilot position since it is not normally exposed to heavy axial forces.

The pilot bearing is effectively enclosed between the input and output shafts and a synchromesh coupling arrangement is provided to allow the direct connection of these two shafts. Consequently, the pilot bearing is shielded from the spray of lubricating oil that normally pervades the interior of the gearbox during operation. It is therefore usual to make some special provision for feeding oil to the pilot bearing.

One such method is to provide a number of drilled holes 26 extending radially inwards from the roots of the teeth on the constantmesh input-shaft gear 7 to connect with the cavity 10 in the end of the input shaft. In operation, the meshing of the gears forces small amounts of oil radially inwards through these holes, from where it flows axially through the pilot bearing to return to the gearbox casing.

Although the flow of oil achieved in this way may be restricted and intermittent it is usually sufficient to maintain effective lubrication of the pilot bearing under normal operating conditions.

In recent years, the increasing use of towed trailers, caravans, etc., has resulted in the more frequent use of gearboxes under conditions of reversed loading, as for example when the vehicle and its towed load descend a steep hill in low gear, using the engine as a means of braking. Under these conditions the axial forces induced by the helical gears are in the opposite directions to those normally applied and therefore the pilot bearing can be subjected to heavy axial forces.

It is been found that, in some cases, the increased demands on lubrication caused by this abnormal operating condition have not been satisfactorily fulfilled by the normal provision for pilot bearing lubrication as described earlier. Consequently, the pilot bearing has sometimes sustained damage in the form of wear or scoring of the bearing surfaces.

The present invention seeks to provide an improved bearing design for use in the pilot position, with provision for better retention of lubricating oil and with increased load capacity.

According to a first aspect of the invention there is provided a tapered roller bearing assembly having inner and outer bearing rings respectively defining inner and outer raceways, a set of tapered rollers rotatably mounted between the raceways and a retaining ring coaxially mounted with respect to either the inner or outer rings, said retaining ring being shaped in such a way as to define, with one end or the other of said rollers, an annular cavity which is operable to act as a temporary reservoir for retaining lubricant supplied to the bearing.

In the preferred embodiment, the lubricating oil for the bearing is supplied at the remote end of the bearing from that at which the retaining ring is situated: lubricating oil thus travels through the spaces between the rollers to collect in the reservoir before finally returning to the main oil circuit.

The inner and outer bearing rings may be separate items, or may be formed integrally with their associated shaft-the inner ring with the output shaft and the outer ring with the input shaft.

The bearing may or may not be equipped with a cage to retain and locate the rollers. In the event that a cage is not used, the retaining ring may be used to provide an additional retention function, namely the mechanical function of retaining the rollers prior to final assembly of the bearing. To this end, the retaining ring is equipped with a lip operable to engage and retain the rollers against an adjacent bearing ring in such a way that the assembly of bearing ring/rollers/retaining ring is held together for assembly together with the remaining parts of the bearing. The use of the retaining ring in this way eliminates the requirement for a cage and enables an increased number of rollers to be fitted, thus increasing the load capacity of the bearing.

Also in the preferred embodiment, the retaining ring is equipped with one or more further lips which are operable to engage with the associated structure in such a way as to retain the ring in place. For assembly purposes, it is preferred that such lips have a degree of radial flexibility to enable them to enter the groove.

In a second aspect of the invention there is provided a lubricant retaining ring for use with the aforesaid bearing, said ring comprising a radially inwardly directed flange portion which when in position in the bearing is operable to define, with the ends of the bearing rollers, an annular cavity which can act as a reservoir for retention of lubricant and means for locating said ring by its perimeter portion in an annular groove formed in the adjacent structure.

In order that the invention may be better understood, an embodiment thereof will now be described by way of example only and with reference to Figures 2 to 6 of the accompanying drawings in which: Figure 2 is a partial side view, partly in section, of a bearing assembly according to the invention; Figure 3 is an enlarged view of the retaining ring forming part of the bearing assembly of Figure 1; Figure 4 is a partial side view of the assembly of Figure 1, but shown in the transportation position, prior to fitting; Figures 5 and 6 are two alternative views of the input shaft and before full assembly of the components; and Figure 7 is a view similar to Figure 4, but showing a version of the bearing in which a cage is utilised.

The bearing assembly is shown fitted within a circular cavity 10 in the form of a blind bore formed axially in the gearbox end of the input shaft 1. The outer end of the aperture is flared outwardly in order to form a tapered outer raceway 11 for the bearing. The inner raceway is formed on an inner bearing ring 12 which is mounted on the end of the output shaft 2 and a set of tapered rollers 14 is fitted between the raceways in the usual manner. Note that no cage is used to retain the rollers, and therefore the maximum number of rollers may be used in order to achieve the maximum load capacity.

A retaining ring 13 is located coaxially with the bearing in a stepped annular groove 15/16 formed in the wall of the cavity 10.

The ring 13 may be moulded from a suitable polymer material such as nylon. Figure 3 shows an enlarged section of the ring.

On one side, the retaining ring has an axially-extending annular lip 17, so shaped and dimensioned as to ensure a tight fit between the ring and the set of rollers at the initial assembly stage of the bearing shown in Figure 4. The ring and in particular the annular lip 17 are designed to ensure that the rollers 14 are effectively retained on the inner ring 12 during storage and handling prior to the final assembly condition shown in Figure 2, and thus eliminate the need for a cage.

The retaining ring has another axiallyextending annular lip 18 on the opposite side to that which engages the rollers. This second lip has a flared outer surface 19 which extends to the largest diameter of the ring.

Both of the annular lips 17, 18 have a degree of radial flexibility, allowing elastic recovery of initial shape after radial deformation.

The main part of the ring 13 comprises a flange 20 extending radially inwards to the smallest diameter of the ring which is somewhat smaller than the diameter of the circle which circumscribes the large ends of the set of tapered rollers 14.

The inner bearing ring 12 of the bearing is formed on its external surface in such a way that the inner raceway lies between two external flanges or ribs 21, 22 located at the ends of the raceway. The distance between these ribs, in a direction parallel to the inner raceway, is slightly greater than the length of the rollers.

At the first stage of assembly, as shown in Figure 4, the rollers are retained on the inner ring in the space between the ribs 21 and 22 by the interference fit of the retaining ring over the large ends of the rollers. In this condition, the rollers are forced against the shoulder presented by the rib 21 on the inner ring.

The input shaft 1 may be designed either as an integral part as shown in Figure 5, or as a composite assembly as shown in Figure 6, to provide the tapered outer raceway for the pilot bearing. In the Figure 6 arrangement, a separate outer ring 23 is fitted into the cavity 10 and forms the outer raceway 11. Whichever the arrangement, the groove 15/16 is formed adjacent to the large end diameter of this tapered outer raceway and faces radially inwards. The groove is flanked on the side farthest from the outer raceway by a tapered land 24, the smallest diameter of which lies next to the groove. The diameter of the widest part 16 of the groove is slightly smaller than the maximum diameter of the ring 13.

On its outside surface the input shaft 1 is provided with gear teeth 25, as aforesaid. A plurality of drilled holes 26 extend radially inwards from positions between the gear teeth to connect with the internal cavity 10 formed in the input shaft adjacent to the small end of the tapered outer raceway.

During assembly of the gearbox, the bearing inner ring assembly shown in Figure 4 is fitted to its seating on the end of the output shaft 2. Similarly, in cases where a separable outer ring 23 is used, this is also fitted to its seating in the end of the input shaft as shown in Figure 6. After this, the input and output shafts are brought into engagement by pressing the two axially together, causing the pilot bearing inner ring assembly to enter the cavity 10 formed in the end of the input shaft. This axial movement proceeds until the outer lip 19 of the ring 13 meets the tapered land 24 on the outer side of the groove 15/16. Continued axial movement causes the outer lip 19 of the ring 13 to deflect radially inwards as it passes across the tapered land.When the outer lip of the ring is axially clear of the tapered land on the input shaft it expands by elastic recovery and seats with a tight fit in the part 16 of the groove 15/16. This occurs upon further relative axial movement which brings a shoulder 30 (see Figure 4) of the ring 13 into contact with a shoulder 31 (see Figure 5) forming the junction between the two parts 15 and 16 of the annular groove in the cavity 10. This prevents any further axial movement of the ring relative to the input shaft in this direction.

Also, since by now the outer lip 19 of the ring has entered the groove, the ring is effectively located and secured in the groove.

The next and final stage of axial movement of the output shaft relative to the input shaft causes the rollers to be prized out of their engagement with the ring 13 by expanding the inner annular lip 17 on the ring. The roller ends are made to separate completely from the ring before axial relative movement is finally arrested by engagement of the rollers with the tapered outer raceway 11.

In this final assembly condition, the ring 13 is held by a radial interference fit inside the groove 15/16. It therefore rotates with the input shaft in operation. The remaining bearing components, i.e. the two tapered raceways and the rollers, are then free to function in the normal manner.

In operation, lubricating oil that is forced into the bearing through the radial holes 26 by the meshing action of the gear teeth passes axially through the bearing, wetting and lubricating the bearing surfaces.

Due to centrifugal action caused by rotation, the oil emerging from the bearing tends to accumulate in the cavity 32 formed between the large ends of the rollers and the flange formed on the radially inside surface of the retaining ring. This cavity acts as a reservoir and retains sufficient oil to provide effective lubrication at all times, regardless of the rate at which it is replenished and regardless of the effect of severe loading conditions caused by the circumstances described earlier. The in ner tip 33 of the flange 20 effectively forms a weir controlling the amount of oil in the reser voir, excess oil flowing through the gap formed between the tip 33 of the flange 20 (see Figure 3) and the rib 22 (see Figure 4), and back to the gearbox casing.

Thus it will be seen that the retaining ring 13 has two distinct retention functions, thereby achieving two benefits from one device: the first retention function is that of retaining lubricating oil for improved lubrication of the bearing and the second is that of retaining the rollers in the initial stage of assembly shown in Figure 4, thus eliminating the need for a cage which in turn means that an increased number of rollers can be used for increased load capacity.

Figure 7 shows, in a view corresponding to that of Figure 4, an alternative form of bearing utilising a cage 27 of conventional design to locate and retain the rollers. The retaining ring 13 is formed with an annular rebate 34 in order to accommodate the large-diameter end of the cage.

Claims (12)

1. A tapered roller bearing assembly having inner and outer bearing rings respectively defining inner and outer raceways, a set of tapered rollers rotatably mounted between the raceways and a retaining ring coaxially mounted with respect to either the inner or outer rings, said retaining ring being shaped in such a way as to define, with one end or the other of said rollers, an annular cavity which is operable to act as a temporary reservoir for retaining lubricant supplied to the bearing.

2. A bearing assembly as claimed in claim 7 wherein the retaining ring is formed with a lip operable to engage and retain the rollers against one of said bearing rings during assembly of the bearing.

3. A bearing assembly as claimed in claim 2 wherein said lip takes the form of an axiallyextending annular lip.

4. A bearing assembly as claimed in claim 3 wherein the lip has a degree of radial flexibility.

5. A bearing assembly as claimed in any one of claims 1 to 4 wherein the retaining ring is formed with a radially inwardly directed flange portion which defines, together with adjacent parts of the bearing, a reservoir for lubricant.

6. A bearing assembly as claimed in any one of claims 1 to 5 including a further lip on said retaining ring which further ring is operable to engage with either the inner or the outer bearing ring to retain the retaining ring in place.

7. A bearing assembly as claimed in claim 6 wherein said retaining ring is engaged with the outer bearing ring in which latter is formed an annular groove in which said further lip lo cates.

8. A bearing assembly as claimed in claim 7 wherein said retaining ring is formed on its annular outer surface with a shoulder which is such as to engage one side of said groove and so locate the retaining ring with respect to the outer ring.

9. A bearing assembly as claimed in claim 8 wherein said further lip extends axially and engages the outer side of said groove.

10. A bearing assembly substantially as hereinbefore described with reference to the accompanying drawings.

11. A lubricant retaining ring for use in the bearing according to any one of the preceding claims, said ring comprising a radially inwardly directed flange portion which when in position in the bearing is operable to define, with the ends of the bearing rollers, an annular cavity which can act as a reservoir for retention of lubricant and means for locating said ring by its perimeter portion in an annular groove formed in the adjacent structure.

12. A lubricant retaining ring as claimed in claim substantially as hereinbefore described with reference to the accompanying drawings.