GB2031554A

GB2031554A - Air impeller assembly for a rotating electrical machine

Info

Publication number: GB2031554A
Application number: GB7931340A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1978-09-09
Filing date: 1979-09-10
Publication date: 1980-04-23
Also published as: DE2839288A1; JPS5537600A; FR2435618A1

Abstract

An impeller (12) is mounted upon a shaft (11) of a machine, e.g. a motor vehicle alternator, by a nut (17), with locating means comprising a machine element (14) and a pulley (15). A bush (25) and resilient elements (23, 24) may be interposed, by means of which axial shaft vibrations are damped, reducing their transmission to the impeller, thereby minimising noise. Alternatively, non-resilient contact between pulley (15) and impeller (12) may be made through an annular shoulder (22) located between diameters (d1, d2) chosen such that the resonant frequencies of the separate members become changed upon assembly,thereby reducing vibration which might otherwise have occurred in use. <IMAGE>

Description

SPECIFICATION Impeller assembly for a rotating electrical machine The invention relates to an impeller assembly for a rotating electrical machine. In present-day conventional types of construction, the impeller is inserted on the shaft of the machine, together with a pulley and, if necessary, a supporting ring and further supporting or retaining members, and is rigidly clamped in position by means of a nut against a stop on the shaft. Vibration analyses have shown that the unwanted emission of noise is caused by very low-amplitude longitudinal oscillations of the machine shaft. These oscillations are transmitted to the impelier, and emit the unwanted noise.

There is provided by the present invention an impeller assembly for rotating electrical machines, comprising the impeller, clamping means for clamping the impeller on the shaft of the machine free from angular displacement thereon; the impeller being provided with a concentric aperture for insertion on the shaft of the machine, and means for supporting the impeller on the machine shaft, wherein the supporting means and, if need be, the clamping means are proportionately constructed so as to clamp or prevent the transmission of longitudinal oscillations of the shaft to the impeller.

In contrast to the known assembly, that according to the present invention has the advantage that, as a result of simple constructionai measures, the mechanicai coupling between the machine shaft and the impeller is damped, and the natural resonance of the impeller in the assembled state is changed to a frequency range in which excitation by the longitudinal oscillations of the impeller shaft ceases to constitute a nuisance.

By accurate selection of the diameter of the contact surface between the pulley and the impeller, a rigid type of construction of the supporting means for the impeller can be effected to change the natural resonance of the impeller in the desired manner. The desired aim may also be achieved by means of an impeller contact surface in the form of a shoulder, which has the added advantage of easier manufacture. If the supports for the impeller are of a resilient nature, the impeller is effectively disengaged from the machine shaft. It is particularly advantageous, in fact, if the impeller is rigidly secured on the machine shaft, for example by means of a bush, but is resiliently supported by the supporting means.

Embodiments of the invention are shown in the drawings, and are further explained in the description hereinafter.

Figures 1 to 4 show possible rigid methods of supporting the impeller; Figure shows a resiliently supported impeller; Figures 6 to 8 show impellers with rigid and resilient supporting means; and Figure 9 shows an impeller with a resilient interlayer.

Figure 1 shows the end of a machine shaft 11, on which there is mounted an impeller 12 with impeller blades 13. Afurther machine element 14 is shown notionally on the same side as the rotor blades 13.

On the other side, a pulley 15 is mounted on the machine shaft 11, and the complete assembly, comprising the impeller 12 and pulley 15, is clamped on the machine shaft 11 by means of a nut 17 via a washer 16. A contact surface 21, of external diameter d1, of the impeller 12 is in planar abutment with the pulley 15. The diameter d1 is accurately selected with reference to the other dimensions of the impeller 12, so that no vibration in the audible frequency range is caused when the machine, which is not shown, is operating.

Figure 2 shows an embodiment in which, instead of the planar surface extending from the outside diameter of the machine shaft 11 to the diameter d1, there is provided only a shoulder 22, whose outside diameter d1 and internal diameter d2 are arranged concentrically about the impeller shaft 11. The shoulder 22 is formed on the impeller 12.

Figure 3 shows an embodiment in which the above-mentioned shoulder 22 is arranged on the pulley 15 and not on the impeller 12.

In the embodiment shown in Figure 4, a pulley 15 manufactured from sheet metal is used. Correspondingly, a first supporting disc 18 for the pulley 15, and a second supporting disc 19 for the pulley 15 and the impeller 12, are provided. The shoulder 22 abuts the second supporting disc 19.

Figure 5 shows an embodiment in which a first resilient disc 23 is inserted between the impeller 12 and the pulley 15, and a second resilient disc 24 is inserted between the impeller 12 and the further machine element 14.

In the embodiment of Figure 6, a bush 25 is inserted on the machine shaft. The bush 25 is supported on one side against the further machine element 14, and, on its other side, against the pulley 15. The first resilient disc 23, the impeller 12, and the second resilient disc 24 are mounted about the periphery of the bush 25. When the nut 17 is screwed onto the shaft 11, the pulley is rigidly clamped to the further machine element 14, whereas the impeller 12, on the other hand, is resiliently retained via the resilient discs 23, 24.

Similarly, in an embodiment incorporating a sheet-metal pulley, as shown in Figure 7, a bush 25, which is retained between the further machine element 14 and the second supporting disc 19, is provided. In this embodiment, the impeller 12 is clamped only via the first resilient disc 23 against the second supporting disc 19. The joints between the first resilient disc 23 and the two abutting members 19, may be made in a known manner by vulcanising, adhesive bonding, injection moulding, or similar means. Such joints are possible also in the case of the other embodiments shown.

In the embodiment according to Figure 8, in which again a solid pulley 15 is used, driver elements 26 are provided. The driver elements 26 may be in the form of pins or bolts, or may be portions, directly formed by injection moulding or vulcanising, with enlargements, of the resilient interlayer. Additional support in the direction of the longitudinal axis of the machine shaft 11 is made possible by special heads 27 on the driver elements 26.

Lastly, Figure 9 shows an embodiment in which the bush 25 and the second supporting disc 19 are combined to form a single member 28, and the impeller 12 is separated from this single member 28 by a resilient interlayer 29.

The length and diameter of the bush 25, and the diameter and thickness of the resilient interlayers 23, 24 and 28, and, if applicable, the pressure of the nut 17, are selected so as to provide an optimal damping effect.

Claims

1. An impeller assembly for rotating electrical machines, comprising the impeller, clamping means for clamping the impeller on the shaft of the machine free from angular displacement thereon; the impeller being provided with a concentric aperture for insertion on the shaft of the machine, and means for supporting the impeller on the machine shaft, wherein the supporting means and if need be, the clamping means are proportionately constructed so as to clamp or pevent the transmission of longitudinal oscillation of the shaft to the impeller.

2. An assembly according to claim 1, for a rotating electrical machine the shaft end of which is screw-threaded, wherein the clamping means is a nut to be screwed on the shaft end.

3. An assembly according to claim 1 or 2, wherein the supporting means are of rigid construction.

4. An assembly according to claim 1 or 2, wherein the supporting means are of resilient construction.

5. An assembly according to any of claims 1 to 4, wherein the contact surface between the impeller and the pulley is of concentric, annular construction, and has a diameter which is accurately selected to match the other dimensions of the impeller and both the impeller and the pulley have a planar surface in the region of the contact surface.

6. An assembly according to claim 5, wherein the width of the annular contact surface is small compared with its external diameter, and it extends substantially in the region of the larger rim of the pulley.

7. An assembly according to claim 6, wherein the contact surface is in the form of a shoulder, and is very small in depth compared with the thickness of the impeller.

8. An assembly according to claim 7, wherein the contact surface is formed on the impelier.

9. An assembly according to claim 7, wherein the contact surface is formed on the pulley.

10. An assembly according to claim 7, wherein the contact surface is formed on a supporting disc which is inserted between the impeller and the pulley.

11. An assembly according to claim 1,2 or 4, wherein the impeller abuts a first resilient disc, which is inserted between the impeller and the pulley and, where applicable, abuts a second resilient disc, which is inserted between the impeller and further machine elements.

12. An assembly according to claim 11, wherein the impeller and the first resilient disc and, where applicable, the second resilient disc are inserted on a bush which is fitted on the machine shaft.

13. An assembly according to claim claim 11 or 12, wherein between the first resilient disc and the pulley there is inserted a first supporting disc.

14. An assembly according to any of claims 11 to 13, wherein at least one of the lateral surfaces-of-at least one of the resilient discs is mechanically rigidly attached to the respective contact surface.

15. An assembly according to any of the preced- ing claims, wherein at least one driver element.

serves as a support means for the prevention of angular displacement.

16. An assembly according to claim 15, wherein the driver element is provided with at least one enlargement for additional securing the pulley in the axial direction of the machine shaft.

17. An assembly according to any of claims 12 to 16, wherein the bush and a supporting disc are integrally formed.

18. An assembly according to claim 17, wherein between the integrally-formed bush/supporting disc member and the impeller there is provided a resilient interlayer.

19. An impeller assembly substantially as hereinbefore described with reference to Figures 1, 2, 3,4, 5, 6,7, 8 or 9 of the accompanying drawings.