GB2055431A

GB2055431A - Relubrication device for shaft bearings

Info

Publication number: GB2055431A
Application number: GB8014356A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1979-05-15
Filing date: 1980-05-01
Publication date: 1981-03-04
Also published as: JPS55152921A; DE2919489A1

Abstract

The relubrication device comprises a reservoir (16) containing a solid lubricant (17) which, upon a rise in temperature in the bearing (12), becomes fluid and enters the bearing race. In an alternative device (Fig. 4 not shown) the lubricant is an oil which on heating passes through a porous sintered metal reservoir closure plate. <IMAGE>

Description

SPECIFICATION Relubrication device for shaft bearings The invention relates to a relubrication device for shaft bearings especially those of rotating electrical machines.

Known relubrication devices have a reservoir which is subjected to a constant pressure, for example, one derived from the force of a compression spring. However, this solution has the disadvantage that the lubricant is fed continuously to the bearing irrespective of the operating values of the electric machine, that is to say, irrespective of, for example, the rotational speed and the temperature of the machine and also not directly in dependence upon the instant of operation.

In all bearings, such as ball bearings, needle bearings and journal bearings, a distinction is made between the useful life and the service life of the bearing. The useful life is generally dependent upon material fatigue and, with correct dimensioning of the bearing, can be made to conform to the useful life of the electrical machine.

On the other hand, the service life is largely dependent upon whether the bearing is always correctly lubricated or not. The aforementioned expensive relubrication devices are generally required in order to maintain the correct state of lubrication for the useful life of the bearing. When relubrication of the bearing has to be dispensed with for reasons of costs and/or space, the service life of the bearing and thus the useful life of the machine are determined by the first and only lubrication of the bearing.

There is provided by the present invention a relubrication device for shaft bearings having a lubricant reservoir, wherein the lubricant of the reservoir is such as to be substantially solid below a predetermined range of temperature, but substantially fluid above the predetermined range of temperature.

Compare with the known devices, the relubrication device in accordance with the invention has the advantage that it is of spacesaving construction and can be manufactured inexpensively. It can be used in virtually all known bearings. Relubrication is effected automatically in dependence upon predetermined and prescribable operating values. The machine bearings are supplied with sufficient lubricant for their entire useful life and at the correct instant. The failure of generators as a result of damage to the bearings can be reduced to a considerable extent, and thus the reliability of the generators can be increased by the device in accordance with the invention, especially when it is used in three-phase generators for motor vehicles.

Individual embodiments of the invention have their special advantages with respect to spatial requirements, optimum adaptation to the particular machine, and their manufacturing costs.

Embodiments of the invention are illustrated in the accompanyin drawings and are described hereinbelow. In the drawings: Figure 1 to 6 respectively show six embodiments, each of which is realised with respect to a three-phase generator for motor vehicles, each Figure showing a fragment of the generator in section. Identical components are provided with the same reference numerals.

After a long period of use, the lubricant, preferably grease which has been introduced into the bearings during assembly is used up. When the grease has been used up, the shaft bearings run hot as a result of the increased frictional losses. This circumstance is utilised to put the relubrication device, in accordance with the invention, into operation. The principle of the invention is that, upon the above-mentioned increase in temperature, the additional lubricant becomes fluid and flows into the race of the bearing.

Fig. 1 shows a bearing hub 11 into which is fitted a roller bearing 12 having an inner race 13 and an outer race 14. The bearing 12 serves to journal a machine shaft 1 5. A recess 1 6 is provided in the bearing hub 11 in the region of the ball race of the bearing 12 and serves as a reservoir for additional lubricant 1 7. The recess 16 can be in the form of a bore or several bores or, alternatively, can be in the form of a groove extending concentrically of the shaft 1 5.

The lubricant 1 7 is solid or pasty in the first instance. When the bearing 12 is running hot, the heat is transferred from the outer race 14 to the bearing hub 11 and thus to the recess 1 6. The lubricant 1 7 becomes fluid upon the increase in temperature and runs into the ball race of the bearing 12.

In the embodiment of Fig. 2, the recess 16 is disposed on the inside of the bearing hub 11 in the region of the radial circumference of the outer race 14. Here also, the recess 1 6 can be a single bore or several single bores or a radial groove. The outer race 14 has a radial duct 1 8 which establishes communication between the recess 1 6 and the ball race of the bearing 12.

Advantageously, the bearing 12 is provided with shields 1 9.

When the bearing is running hot, the previously solid lubricant 17 in the recess 16 serving as a reservoir becomes fluid and flows through the duct 18 and into the ball race of the bearing 12.

In a variant of the embodiment of Fig. 2, the cut 18 can be in the form of a radial groove. The associated shield 1 9 is then omitted. The mode of operation is the same: upon a considerably rise in temperature, the liquid lubricant 1 7 flows through the radial groove and into the ball race of the bearing 12.

In contrast to the embodiment of Fig. 2, Fig. 3 shows an embodiment in which the recess 1 6 acting as a reservoir is in the form of a blind axial bore in the bearing hub 11. Advantageously, several of these bores 1 6 are provided concentrically of the machine shaft 1 5. The bores are covered by an annular shield 21. The shield 21 abuts flatly against the bearing hub 11 concentrically of the shaft 1 5. Radially extending grooves 22 are provided in the shield 21 and establish communication between the bores 1 6 and the ball race of the bearing 1 2.

Upon a rise in temperature, the lubricant 17, which is solid in the first instance, becomes fluid and flows to the bearing 12 through the groove 22.

Fig. 4 shows an embodiment which is similar to the embodiment of Fig. 3. In the embodiment of Fig. 4, a liquid lubricant, such as oil, is accommodated in the bore 16 serving as a reservoir. The bore 1 6 is sealed by means of a plug 23, such as a small plate made from sintered metal.

Upon an increase in temperature caused by a hot-running bearing 12, the oil 1 7 percolates through the sintered metal plate 23 and then flows through the groove 22 and the ball race of the bearing 12.

In the embodiments of Fig. 3 and Fig. 4, the bore 16 can be provided with a cover made from a resilient material. The form of the cover is then substantially the same as that of the sintered metal plate 23 of Fig. 4. The cover of resilient material serves to equalise the pressure when the generator is operating satisfactorily.

In the embodiment of Fig. 5, the bore 1 6 serving as a reservoir is disposed centrally in the machine shaft 1 5. In this solution also, either a solid lubricant 1 7 or a liquid lubricant can be accommodated in conjunction with a porous cover 23 or, alternatively, a solid or liquid lubricant can be accommodated in conjunction with a resilient cover. The bore could also be arranged radially.

When the bearing 1 2 is running hot, the heat is transferred to the shaft 50 by way of the inner race 1 3 and the relubrication operation is initiated in the manner already described.

Fig. 6 shows an embodiment in which a centrifugal disc 24 is mounted on the shaft 1 5.

The centrifugal disc has a trough-shaped cross section. The trough-shaped interior of the centrifugal disc 24 serves as a reservoir for the solid lubricant 17.

When the bearing 12 is running hot, the lubricant 1 7 becomes fluid and, during rotation of the shaft 1 5, is centrifuged into the ball race of the bearing 12 by centrifugal force.

Claims

1. A relubrication device for shaft bearings having a lubricant reservoir, wherein the lubricant of the reservoir is such as to be substantially solid below a predetermined range of temperature but substantially fluid above the predetermined range of temperature.

2. A device as claimed in claim 1 , wherein the reservoir is disposed in a recess in the bearing hub.

3. A device as claimed in claim 1, wherein the reservoir is disposed in a recess in the shaft.

4. A device as claimed in claim 1 or 2, wherein the reservoir is an annular groove which is disposed concentrically of the shaft in the region between the inner race and the outer race of the bearing.

5. A device as claimed in claim 2, wherein the outer race of the bearing is provided with at least one duct, and the recess communicates with the duct.

6. A device as claimed in claim 4, wherein the duct is a radial groove.

7. A device as claimed in one of the claims 1 to 3, 5 or 6, wherein the reservoir is a radial bore.

8. A device as claimed in one of the claims 1 to 3, 5 or 6, wherein the reservoir is an axial bore.

9. A device as claimed in claim 7 or 8, wherein the reservoir comprises a plurality of cqmponent reservoirs.

10. A device as claimed in claim 8 or claims 8 and 9, wherein the bore opens externally of the hub and there is provided a bearing shield which includes at least one depression acting as conveying connection between the reservoir and the bearing.

11. A device as claimed in any of the preceding claims, wherein the reservoir exit is closed by means of a porous cover.

12. A device as claimed in any of the preceding claims 1 to 10, wherein the reservoir includes, in addition to the lubricant, a resilient cover for equalisation of pressure.

13. A device as claimed in claim 1, wherein the reservoir is formed by a cavity in a centrifugal disc which is mounted on the shaft.

14. A relubrication device for a shaft bearing substantially as hereinbefore described with reference to any of Figures 1 to 6 of the accompanying drawings.