GB2387205A

GB2387205A - Lubricated taper roller bearing assembly

Info

Publication number: GB2387205A
Application number: GB0302726A
Authority: GB
Inventors: Dirk-Olaf Leimann
Original assignee: Hansen Transmissions International NV
Current assignee: ZF Wind Power Antwerpen NV
Priority date: 2002-02-08
Filing date: 2003-02-06
Publication date: 2003-10-08
Anticipated expiration: 2023-02-06
Also published as: GB2387205B; AU2003209547A1; GB0302726D0; GB0202944D0; WO2003067108A1

Abstract

The invention provides a lubricated taper roller bearing assembly comprising a taper roller bearing 14 arranged in series with a screw pump 17, said bearing 14 and screw pump 17 in use being submersed in lubricant, said screw pump 17 being rotatable in unison with one of the inner and outer bearing rings which is rotatable relative to the general body of lubricant contained in a lubricant sump, and said screw pump 17 being positioned axially at that side of the taper roller bearing 14 at which the bearing rollers have their maximum diameter. Preferably said screw pump 17 is arranged to urge lubricant to flow in a directional way from the taper roller bearing. The invention also provides a gear unit which is for operation in either of two direction of rotation, wherein two pumps (65,66, Fig 8) may be provided and arranged such that one provides forced lubrication when drive in one direction and the other provides forced lubrication when drive is on the opposite direction.

Description

LUBRICATED TAPER ROLLER BEARING ASSEMBLY

This invention relates to a lubricated taper roller bearing assembly and in particular, though not exclusively, to a lubricated taper roller bearing assembly for use in an industrial type gear unit.

It is known that taper roller bearings tend to support lubricant, i.e. promote, flow from the small end of each roller to the larger end of each roller, as depicted by Figure 1. The pumping action effected by the taper roller bearing is not, however, able to create sufficient pressure for use in pressure lubrication of component parts, such as other bearings of a gear unit, or to pump liquid lubricant from a lower point to a higher point from which lubricant might then fall under gravity to parts requiring lubrication.

In industrial gear units of the kind having a vertical shaft arrangement the lower bearings typically are always submersed in lubricant. Lubrication of the gears and upper bearings can be achieved also by immersing them in lubricant, but that undesirably leads to relatively high thermal losses. Alternatively a shaft or motor driven pump can be connected to the gear unit to provide a direct flow of lubricant from an oil bath at the bottom of the gearbox housing to other bearings and gears. However the need to provide an external pump adds undesirably to costs. It is also known for industrial gear units with vertical shafts to be provided with grease type lubrication for the upper bearings and to use a liquid lubricant for the gears and lower bearings, said gears and lower bearings being submersed in the liquid lubricant. This however also creates significant thermal losses which are greater than those associated with a gear unit having a minimum lubricant bath which submerses only lower bearings. Also in many instances the use of two different lubricants in one gear unit is unacceptable.

A further disadvantage of known procedures for pumping lubricant is that at low ambient temperatures the viscosity of the lubricants becomes high, and in order to handle high viscosity lubricants special pump designs are required, involving additional expense.

One object of the present invention is to provide a lubricated taper roller bearing assembly in which the aforedescribed difficulties are mitigated or overcome. In accordance with one aspect of present invention a lubricated taper roller bearing assembly comprises a taper roller bearing arranged in series with a screw pump, said bearing and screw pump in use being submersed in lubricant, said screw pump being rotatable in unison with one of the inner and outer bearing rings which is rotatable relative to the general body of lubricant contained in a lubricant sump, and said screw pump being positioned axially at that side of the taper roller bearing at which the bearing rollers have their maximum diameter.

The inner ring of the taper roller bearing may be carried by a rotatable shaft, such as a high speed shaft of an industrial gear unit, and said screw pump (hereinafter referred to also as a vane pump) may be secured to an end region of the shaft adjacent to the taper roller bearing.

Preferably the outer diameter of the screw pump is within + 30% or more preferably within + 20% of the inner diameter of the bearing outer member or the so-called 'cup' of the bearing at its adjacent end, i.e. end closest to the screw pump. Most preferably the outer diameter of the screw pump is equal to the inner diameter of the bearing cup.

Preferably said screw pump is arranged to urge lubricant to flow in a direction away from the taper roller bearing, thereby to augment the lubricant flow inherently induced through the bearing in consequence of the tapered shape of the bearing rollers.

Lubricant conduit means may be provided in the vicinity of the screw pump, at a down stream side, i.e. at the side of the screw pump furthest from the taper roller bearing, and arranged to direct a flow of pressurised lubricant to an upper region, for example an upper region of the housing of an industrial gear unit. The conduit for lubricant may direct the lubricant to a position at which it is directed under pressure to another bearing or, for example, to a position from which it may flow under gravity onto a bearing or toothed gear.

In the case of a gear unit which is for operation in either of two directions of rotation, two vane pumps may be provided and arranged such that one provides forced lubrication when drive is in one direction and the other provides forced lubrication when drive is in the opposite direction. An additional pump may be mounted on another existing internal shaft, particularly in the case of a multi-stage gear unit, and- may be arranged to supply forced lubrication through a second conduit leading to an upper bearing. A valve, such as a simple flap valve, may be provided so that the forced flow of lubricant to a bearing from one pump is not adversely affected by the actions of the other pump. Alternatively, and especially if two shafts are not available each for conveniently mounting of a vane pump, two vane pumps of opposite helical disposition may be provided on a common shaft and a fluid barrier, such as an annular washer, may be provided between the two pumps so that the pressurising effect of one vane pump is not adversely affected by the opposite action of the other vane pump.

If two pumps are mounted on respective shafts that are rotatable at different speeds, one pump (that on the lower speed shaft) may be larger than the other such that, for example, substantially the same flow of forced lubricant is achieved irrespective of the direction of rotation.

The invention further provides a multi-stage gear unit comprising a shaft rotatably supported by axially spaced ball or roller bearings, at least one of said

bearings in use normally being immersed in lubricant, and substantially adjacent said immersed bearing a vane pump rotatable in unison with the shaft to cause lubricant to flow towards a rotatable compnent of the gear unit positioned above the normal level of said lubricant.

Preferably the multi-stage gear unit comprises a shaft rotatably supported by a.lubricated taper roller bearing assembly of the present invention. The shaft preferably is a high speed shaft, e.g. an output shaft.

One embodiment of the invention will now be described, by one example only, with reference to the accompanying diagrammatic drawings in which: Figure 2 is a sectional view of a gear unit comprising a lubricated taper roller bearing assembly in accordance with the present invention; Figure 3 shows an end view of the screw pump of Figure 2; Figure 4 is a view in the direction of the arrow X of Figure 3; Figure 5 is a view in the direction of the arrow Y of Figure 3; Figure 6 is a section of line XX of Figure 5, and Figure 7 and 8 each show sectional views of gear units in accordance with further aspects of the present invention.

A gear unit 10 (see Figure 2) comprises a housing 11 having a high speed shaft 12 rotatably supported therein by means of a pair of axially spaced taper roller bearings 13, 14 arranged in an O configuration in which the bearing rollers each increase in diameter in a direction away from the other bearing of the pair.

The bearing 14 is positioned inwards from an end 15 of the shaft 13, and a screw pump vane formation 16, mounted on a support sleeve 17, is fitted tightly to the end of the shaft 12.

The shaft 12 in use extends vertically with bearing 13 positioned above bearing 14. The housing is provided with a fluid flow channel (not shown) which extends from a lubricant chamber 20 surrounding the screw pump vane 16 to a

s position near to the upper part 21 of the housing from which the channel directs a flow of pressurised lubricant on to the upper bearing 13. Optionally pressurized lubricant may be supplied to other positions in an upper region of the gear unit housing above the normal level 23 of lubricant contained in the gear unit housing.

The construction of the screw pump is shown in more detail with reference to Figures 3 to 6. The helically extending vane is provided at a pitch angle which preferably lies in the range 70 degrees to 89.7 degrees relative to the axis of rotation, and in the illustrated embodiment is at pitch angle of 86 degrees. As shown in Figure 6 the vane is of a tapered cross section, reducing in axial thickness from its root region 31 to the tip region 32.

In this embodiment the radial diameter D of the screw pump is equal to the inner diameter of the bearing outer member or 'cup' at the axial end, closest to the pump, i.e. the diameter at point P shown in Figure 1.

In accordance with the invention the radial diameter D of the screw pumps may be within 30% or more preferably within 20% greater or smaller that the diameter at point P commensurate with the screw pump being freely rotatable within the adjacent bearing housing.

In this embodiment the helical vane 16 has a right hand twist about the rotational axis of the shaft 12. To achieve a pumping action with the bearing mounted to the right hand side of the vane as shown in Figure 4, i.e. proximate to the vane end 26, (and with the larger diameter ends of the bearing rollers being closest to the vane 16) the shaft is rotated anti-clockwise as viewed from the bearing in a direction towards the shaft end 15. Thus the vane pump urges lubricant to flow in a direction away from the bearing, this adding to the flow inherently arising in the bearing, in the same direction, due to the direction in which the roller bearings taper. More generally. when the vane is viewed in a direction from the bearing to the shaft end, the direction of shaft rotation should

4 6 be opposite that direction in which the vane extends helically about the shaft. In consequence lubricant which inherently tends to flow naturally through the taper roller bearing in the direction of increasing diameter of the bearing rollers is in effect additionally drawn through the taper roller bearing by the action of the screw pump, and is pressurised to enable it to be fed to an upper region of the gear unit housing.

if the shaft rotates in a direction opposite to that of the shaft 12, a vane with a left hand twist is employed.

In a second embodiment of the invention a gear unit 40 (see Figure 7) comprises a high speed shaft 41 which is rotatable either clockwise or anti-

clockwise via an intermediate shaft 42. The high speed shaft is provided with an O configuration of axially spaced taper roller bearings 43,44 and a vane pump 45 corresponding to those of the high speed shaft 12 of the first embodiment. The intermediate shaft 42 is similarly supported by bearings 46,47 and a vane pump 48 is provided under the lower bearing 47. Because the shaft 42 rotates in a direction opposite that of shaft 41, the vane pump 48 has the vane thereof extending in an opposite hand to that of pump 45.

The gear unit housing 49 locates bearing end caps 50 each provided beneath a vane pump and provided with an aperture 51 to which a feed pipe (not shown) is connected to conduct pressurised lubricant from the pump to one or more of the upper bearings 43,46. A flap valve (not shown) is provided in each feed pipe to ensure that lubricant supplied through one feed pipe cannot be drawn down through the other feed pipe, away from an upper bearing, by action of the vane pump to which that other feed pipe is connected.

In a third embodiment (see Figure 8) a gear unit 60 comprises a high speed output shaft 61 which is horizontally mounted and supported in an O configuration of taper roller bearing 62,63, immersed in lubricant 64. The shaft is intended, in

use, to be rotatable either clockwise or anti-clockwise. Each end of the shaft is provided with a vane pump 65,66 and an apertured bearing end cap 67,68 in a manner corresponding to the arrangement described with reference to Figure 7.

Similarly, one vane pump has the vane thereof extending in an opposite sense to that of the other pump, and one-way valves are provided in feed pipes to ensure that feed from one pump is not adversely affected by action of the other pump.

A particular advantage of the use in a gear unit of a screw pump as hereindescribed is that the pump is contained wholly within the gear unit housing, without need for external connection or provision of additional and or expensive equipment such as an external pump.

Claims

1. A lubricated taper roller bearing assembly comprising a taper roller bearing arranged in series with a screw pump, said bearing and screw pump in use being submersed in lubricant, said screw pump being rotatable in unison with one of the inner and outer bearing rings which is rotatable relative to the general body of lubricant contained in a lubricant sump, and said screw pump being positioned axially at that side of the taper roller bearing at which the bearing rollers have their maximum diameter.

2. A lubricated taper roller bearing assembly according to claim 1, wherein the outer diameter of the screw pump is within 30% smaller or greater than the inner diameter of the outer member or 'cup' of the bearing at that end which is axially closest to the screw pump.

3. A lubricated taper roller bearing assembly according to claim 2, wherein the outer diameter of the screw pump is within 20% smaller or greater than the inner diameter of the outer member or 'cup' of the bearing at said end.

4. A lubricated taper roller bearing assembly according to claim 3, wherein the outer diameter of the screw pump is equal to the inner diameter of the outer member or'cup'of the bearing at said end.

5. A lubricated taper roller bearing according to any of claims 1 to 4, wherein the screw pump is arranged, in use, to urge lubricant to flow in a direction away from the taper roller bearing.

6. A lubricated taper roller bearing assembly according to any of claims 1 to 5, wherein the direction of rotation of the screw pump as viewed in a direction from that end of the screw pump closest to the bearing to that end furthest from the bearing is opposite the direction in which the vane extends helically relative to said axis of rotation.

7. A lubricated taper roller bearing assembly according to anyone of the preceding claims and comprising a shaft rotatably supported by a pair of axially spaced taper roller bearings arranged in an O configuration.

8. A lubricated taper roller bearing assembly according to claim 7, wherein the screw pump is positioned axially outwards of said axially spaced pair of taper roller bearings.

9. A lubricated taper roller bearing assembly according to claim 7 or 8, wherein said screw pump is secured to said shaft.

10. A lubricated taper roller bearing assembly according to any of claims 7 to 9, wherein a screw pump is positioned axially outwards of each of the taper roller bearings.

11. A lubricated taper roller bearing assembly according to anyone of the preceding claims wherein the screw pump is positioned substantially adjacent that side of said taper roller bearing at which the bearing rollers have their maximum diameter.

12. A lubricated taper roller bearing assembly according to anyone of the preceding claims and comprising conduit means an end of which is in the vicinity of the screw pump at a down stream side of the screw pump.

13. A lubricated taper roller bearing assembly according to claim 11, wherein said conduit means is operable in use to direct a flow of lubricant to a position above the normal level of lubricant contained in said lubricant sump.

14. A lubricated taper roller bearing assembly according to anyone- of the preceding claims wherein the screw pump comprises a vane which extends helically at a pitch angle greater than 70 degrees relative to the axis of rotation of the pump.

15. A lubricated taper roller bearing assembly according to claim 1 and substantially as hereinbefore described.

16. An industrial type gear unit comprising a lubricated taper roller bearing assembly according to anyone of the preceding claims.

17. An industrial type gear unit according to claim 16, wherein the screw pump is mounted for rotation about a vertical axis.

18. An industrial type gear unit according to claim 16 or claim 17 and comprising two vane pumps one to provide forced lubrication when drive is transmitted through the gear unit in one direction of rotation, and the other to provide forced lubrication when drive is transmitted through the gear unit in a direction opposite said one direction.

19. An industrial type gear unit according to claim 18, said gear unit being a multi-stage gear unit comprising a high speed shaft and an intermediate shaft, and each of said high and intermediate speed shafts being provided with a screw pump.

20. An industrial type gear unit according to claim 16 and substantially as hereinbefore described.

21. A multi-stage gear comprising a shaft rotatably supported by axially spaced ball or roller bearings, at least one of said bearings in use normally being immersed in lubricant, and substantially adjacent said immersed bearing a vane pump rotatable in unison with the shaft to cause lubricant to flow towards a rotatable component of the gear unit positioned above the normal level of said lubricant.

22. A multi-stage gear unit according to claim 21 and comprising a shaft rotatably supported by a lubricated taper roller bearing assembly according to claim 1.

23. A multi-stage gear unit according to claim 21 or claim 22, wherein the shaft is a high speed output shaft.