GB2207956A

GB2207956A - Electric motor with oil slinger

Info

Publication number: GB2207956A
Application number: GB08716518A
Authority: GB
Inventors: Patrick Shui-Chung Wang; Georg Strobl
Original assignee: Johnson Electric Industrial Manufactory Ltd
Current assignee: Johnson Electric Industrial Manufactory Ltd
Priority date: 1987-07-14
Filing date: 1987-07-14
Publication date: 1989-02-15
Also published as: DE8809000U1; CN2037509U; JPS6434858U; GB8716518D0

Abstract

A PMDC motor has an oil slinger 29 between a commutator 4 and bearing 11. The slinger 29 is in the form of a flat mylar washer whose internal diameter is smaller than the outer diameter of the motor shaft 2. As the slinger 29 is forced onto the shaft 2 it adopts a dished configuration. To prevent the slinger 29 contacting other component parts and flipping over to a configuration convex to the bearing 7 a stop (33,36,39) is provided to limit the axial movement of the shaft 2 in a supporting bearing 11. <IMAGE>

Description

Electric motor with slinger The present invention relates to an electric motor, in particular to a fractional horsepower permanent magnet direct current (PMDC) motor. Such motors commonly have a slinger mounted on the motor shaft between a bearing and a commutator or armature of the motor. The slinger helps prevent oil from migrating along the shaft on to the commutator by throwing the migrating oil radially away from the shaft.

The effectiveness of the slinger may be improved if it is dished so as to be concave towards the bearing. However a dished slinger may be more expensive than a planar slinger.

The present invention provides an electric motor having an oil slinger mounted on a cylindrical support, wherein the slinger comprises a generally flat disc having a central aperture for receiving the support, the aperture having a diameter slightly less than that of the outer diameter of the support, the arrangement being such that when - the disc is mounted on the support it is dished.

As the central aperture in the slinger is expanded it causes the slinger to adopt a dish shaped configuration.

Hence by providing an interference fit between the support and the slinger, it is possible to use a planar slinger to provide the advantages of a dish shaped slinger.

Other preferred features and advantages of the invention will be apparent from the following description and the accompanying claims.

The invention will be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view through a PMDC motor showing a first embodiment of the invention, Figure 2 is an enlarged detailed view of the area circled A in Figure 1; Figure 3 is a view similar to Figure 2 showing a second embodiment of the invention; Figure 4 is a view similar to Figure 2 showing a third embodiment of the invention; and Figure 5 is a view similar to Figure 2 showing a fourth embodiment of the invention.

Referring to Figure 1, a fractional horsepower permanent magnet direct current motor 1 is illustrated.

The motor comprises a motor shaft 2 which carries a wound armature 3 and commutator 4. The commutator 4 and armature 3 are mounted fast on the shaft and the armature is wound and connected to the commutator in the manner generally known in the art. Tangs 23 on the commutator are forged to wires 26 which formthe coil windings of the armature.

The shaft 2 is mounted in a cylindrical metal casing 5.

Casing 5 is closed at one end by an integrally formed end plate 6. End plate 6 carries a bearing 7 in a housing 8, the shaft 2 being journalled in the bearing 7. A brass collar 24 is a force fit on the shaft 2 to limit the axial movement of the shaft through bearing 7. A washer 25 is mounted on the shaft between the brass collar 24 and bearing 7.

End plate 6 has a plurality, typically 4, of circumferentially extending slots 9 for ventilation of the inside of the motor.

A plastics end cap 10, typically of nylon, houses a self aligning sintered bearing 11 which is held in place by axially extending tabs 12 of a washer 13 which is pressed into the end cap. The end cap supports brush gear comprising a pair of carbon brushes 14 (one is seen in Figure l) which are urged against the commutator 4 by brush leaves (not seen in Figure 1) which are connected to power supply tags 15.

The brush leaf/tag assemblies are held on the end cap 10 by rivets 16, 17.

In the example shown the casing 5 carries two permanent magnets 18, which each bear at one axial edge 20 against a respective tang 19 and are urged apart at their other axial edges by a 'U' shape spring 21.

Circumferentially extending slots 22 are provided in the casing 5 in the region between the brushes 14 and armature 3 for ventilation.

The improvement provided by the present invention resides in the slinger 29 on shaft 2, between the bearing 11 and commutator 4.

The slinger 29 is formed from a mylar disc. The disc is annular and has a central aperture 30 which has a diameter slightly less than the outer diameter of the shaft 2. As the disc is pushed onto the shaft 2 during the assembly of the motor, the disc will adopt a dish-shaped configuration generally as shown. It will be appreciated that configuration of the disc is bistable, it may bow to the left or right as seen in figure 2 and may be flipped between the two positions. The disc is arranged to be concave towards the bearing. In use, any oil migrating along the shaft 2 from the bearing 11 will spread across the opposing face 31 of the slinger and be thrown radially outward as it reaches the outer periphery 32 of the slinger as the motor rotates.If the motor is installed with its shaft vertical, the commutator uppermost, the dish shape will serve to collect any oil migrating downwards from the bearing 11 when the motor is not in use.

Because of the bistable configuration of the slinger 29, if it touches against the bearing 11 or the end cap 10 it may flip over. A force fitted collar may be provided on the shaft 2 between the slinger 29 and bearing 11 to limit the axial movement of the shaft through the bearing.

Figures 3 to 5 show other arrangements for limiting the axial movement of the shaft 2 to prevent flip over of the slinger.

In Figure 3, a blind housing 34 is formed in the end cap for the bearing 11, the housing incorporating a thrust plate 33.

In Figure 4 , the commutator base 35 which supports the segments 27 is provided with a cylindrical boss 36 which extends along the shaft 2 towards the bearing 11. The slinger 29 is mounted on the boss 36 with its peripheral edge 32 behind the forward end 37 of the boss 36. A thrust washer 38 is provided between the boss 36 and the bearing 11.

In Figure 5, the slinger 29' is provided with an integrally formed cylindrical boss 31 which extends along the shaft 2 towards the bearing 11. The boss 39 extends just beyond the plane of the outer periphery 32' of the slinger 29'. A thrust washer 38 is provided between the slinger 29 and bearing 11.

The slinger 29 is preferably of mylar but other suitable material may be used.

A slinger may be provided between the armature 3 and bearing 7. It may be provided between the collar 24 and the armature. Collar 24 may be omitted and other arrangements for inhibiting axial movement of the armature towards the bearing 7 adopted. For example the armature may have a boss extending towards the bearing 7 and carrying the slinger.

Various modifications may be made to the embodiments described and it is described to include all such modifications as fall within the scope of the accompanying claims.

Claims

1. An electric motor having an oil slinger mounted on a cylindrical support, wherein the slinger comprises a generally flat disc having a central aperture for receiving the support, the aperture having a diameter slightly less than that of the outer diameter of the support, the arrangement being such that when the disc is mounted on the support it is dished.

2. An electric motor as claimed in claim 1, wherein means is provided to limit axial movement of the support relative to another component part of the motor to prevent the slinger contacting the said component part.

3. An electric motor as claimed in claim 1 or 2, wherein the cylindrical support is a shaft of the motor.

4. An electric motor as claimed in any one of claims 1 to 3, wherein a thrust plate is provided to limit axial movement of the shaft.

5. An electric motor as claimed in claim 1 having a commutator, wherein the support comprises a boss formed on an end of the commutator.

6. An electric motor as claimed in claim 1 having an armature, wherein the support comprises a boss formed on an end of the armature.

7. An electric motor as claimed in claim 5 or 6, wherein the boss extends along the shaft in a forward direction, the slinger being concave in the forward direction, and the boss extends beyond the forward extent of the outer periphery of the slinger.

8. An electric motor as claimed in claim 1, wherein the slinger has a cylindrical boss about the central aperture, the boss extending along the support in a forward direction, the slinger being concave in the forward direction and the boss extending beyond the outer periphery of the slinger in the forward direction.

9. An electric motor as claimed in any one of claims 1 to 8, wherein the slinger is of mylar.

10. A fractional horsepower PMDC motor as defined in any one of claims 1 to 7.

11. A fractional horsepower motor substantially as hereinbefore described with reference to Figures 1 and 2 or Figure l as modified by Figure 3, 4 or 5.