GB2033673A

GB2033673A - Supporting electrical machines

Info

Publication number: GB2033673A
Application number: GB7936276A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1978-10-20
Filing date: 1979-10-19
Publication date: 1980-05-21
Also published as: FR2439498A2; DE2845666A1

Abstract

The housing of an electrical machine comprises a casing (11) receiving the stator, and two end shields; with a bracing arm (31) and/or a pivot arm (29) incorporated in the profiled casing section. The construction of the casing (11) is such that drawn profiled-section material may be used. The end plates, which support the rotor bearings, may be mounted on the casing by means of screws received in slots 33. Such an electrical machine, in the form of an alternator, is suitable for use in motor vehicles. <IMAGE>

Description

SPECIFICATION Electrical machine The invention relates to electrical machines, such as alternators for motor vehicles.

In particular, alternators for motor vehicles are generally provided with a bracing arm and a pivot arm. The bracing arm and the pivot arm serve for adjustable attachment of the alternator to the internal combustion engine of the motor vehicle. Conventionally, the bracing arm and the pivot arm are cast integrally with the same end shield of the alternator. It is however necessary for the bracing arm to have different positions relative to the pivot arm, for different types of vehicles, and this necessitates a different end shield for each application. This results in an undesirable variety of types of alternators.

Since the centre of gravity of the machine, especially that of the alternator, does not lie in the region of the end shield, but in the region of the centre of the complete machine, wear phenomena, due to vibrational stresses, occur in conventional machines.

Moreover, secure clamping of the machine is not ensured.

An electrical machine according to the invention comprises a housing having a casing and two end shields attached to opposite ends thereof, the housing also having a pivot arm and a bracing arm of which at least the pivot arm is a constituent part of the casing, the machine further comprising a stator mounted in the casing and a rotor journalled in the two end shields.

Thereby, the pivot arm can be arranged substantially below the centre of gravity of the machine, and is both reliable in service and inexpensive to manufacture. A further advantage is that, for conventional assembly requirements, only a single variety of parts needs to be produced and held in stock.

The bracing arm can be likewise formed as a constituent part of the casing. Such an arrangement of the bracing arm is also reliable in operation and inexpensive. The casing can be drawn or extruded.

An extruded component has greater strength as compared with the strength of a casting, since the extruded component is substantially free of shrinkage cavities and has a closer-grained structure, and there is less danger of thermal cracks. In the case of an extruded component, the material-saving cylindrical inner and outer dies are used to advantage, and the dies do not have a tendency to lift. Forming costs are less, and the desired die can be produced quickly; consequently, lead times, even for the manufacture of a variety of types requested, are short, and costs low. Manufacture of the casing from profiled bar material is substantially more economical than single-piece production, for example, of castings. An extruded component ensures a smooth, aesthetically attractive surface.The necessary attachment holes for the end shields may be embodied in the extruded section; no further machining is then necessary. Mounting arms on the intermediate housing permit an almost planar construction of the end shields, and low-cost manufacture of the end shields is accordingly possible. If the casing is constructed, for example, with a hexagonal cross-section, it is possible, without additional cost, to provide cooling passages for the stator. Because of the hexagonal cross-section, the arms for the desired mounting positions can be arranged in steps of 60 in either direction. The position of the electrical connections may also be moved in 60 steps in either direction; consequently, substantial scope is provided for the desired mounting positions.Furthermore, an angular-for example, a hexagonal cross-section of the intermediate casing enables cooling passages, for cooling of the stator, to be provided without additional cost.

The invention is further described, by way of example, with reference to the drawings, in which Figure 1 is a partially sectional side-elevational view of an alternator, Figure 2 a front elevational view of a first embodiment of alternator casing, Figure 3 is a similar view of a second embodiment and also indicates a third embodiment of casing, Figure 4 an elevational view of the alternator from the driving end, and Figure 5 a rear elevational view of the alternator.

In the side-elevational view of Figure 1, a stator 12, having a statorwinding 13, is supported in an alternator casing 11. The stator 12 is press-fitted into the casing 11, and thereby immovably clamped. A first end shield 14 and a second end shield 15 are attached to the casing 11 at the driving and slip-ring ends thereof, respectively. A machine shaft 18 is journalled in bearings 16 and 17 in the end shields 14 and 15. A rotor is mounted on the machine shaft 18 and has a core 19, pole wheels 21 and an excitation winding 22. The ends of the excitation winding 22 are connected to slip rings 23. Avoltage-regulator and brush-holder unit 24 is operatively associated with the slip rings 23. A rectifier arrangement 25 is serially connected to the stator winding 13.A fan impeller 26 and a belt pulley 27 are placed on the driving end of the machine shaft 18, these components being clamped on the machine shaft 18 by means of a nut 28, which is screwed on the end of the machine shaft 18.

The casing 11 is provided with a pivot arm 29 and a bracing arm 31.

Figure 2 illustrates a first embodiment of the casing 11 (notthatshown in Fig. 1). In particular, it can be seen that the casing 11 has a hexagonal radially symmetrical cross-section of configuration in profile.

In this first embodiment, only the pivot arm 29 is formed integrally with the casing 11. In each of the six corners is a slot 32, which opens out from a core hole 33 which serve to receive a screw for the attachment of the end shield. At each side of each slot 32 is a fixing limb 34, which has a plurality of functions.

First, the fixing limbs 34 provide additional abutment surfaces for the end shields 14 and 15; secondly, their sides 35 facing towards the centre of the crosssection, together with the intermediate inner wall portions 36 of the casing 11, are arcuate to define a core bore for retention of the stator 12, which is press-fitted in the casing 11.

Figure 3 shows a second embodiment, and, in broken lines, a third embodiment, of the casing 11. In the second embodiment, the pivot arm 29 and the bracing arm 31 lie on diametrically opposite sides of the central point 37 of the profile. This embodiment is also shown in Figure 1. Because of the radially symmetrical shape of the casing relative to the central point 37 of the profile, it is readily possible for the bracing arm 31 to be formed, alternatively, at other points of the profile, 60" offset in either direction. The second embodiment, has, as shown in broken lines, a bracing arm 31', which is offset 60" to the left. Further embodiments, in which the bracing arm 31 is offset a further 60 , are, of course, possible.

Figure 4 is an end elevational view of an alternator from the driving end, after removal of the impeller 26, the belt pulley 27, and the nut 28. In the foreground there is shown the first end shield 14. Behind it are seen the pivot arm 29 and the bracing arm 31 of the second embodiment. In this case also, the first end shield 14 has a hexagonal radially symmetrical configuration. In the end shield 14 boreholes 38 are provided at all of the six corners. The end shield 14 is secured to the casing 11 by means of four screws 39, which are situated opposite the core holes 33 in the casing 11. Tapping is unnecessary if self-threading or self-tapping screws are used.

Figure 5 is a view of the alternator from the rear.

On its rear end the alternator is provided with a cover 41 for protection of the electrical components.

The second embodiment of casing 11 is again shown as an example. The cover 41 is, for example, secured to the casing 11 by means of three screws 42. Alternatively, it is possible to attach the cover 41 by means of one screw to the casing 11, and, by means of additional clips, to the rectifier 25 or the casing 11.

Three screws 43, by means of which the second end shield 15 is secured to the casing 11, are covered by the cover 41. Apertures 44 (Fig. 4) in the first end shield 14, and apertures 45 (Fig. 5) in the cover 41, serve for ventilation of the alternator.

The profile of each of the embodiments of intermediate casing 11 is such that the casing may be made from drawn or extruded section.

Claims

1. An electrical machine comprising a housing having a casing and two end shields attached to opposite ends thereof, the housing also having a pivot arm and a bracing arm of which at least the pivot arm is a constituent part of the casing, the machine further comprising a stator mounted in the casing and a rotor journalled in the two end shields.

2. A machine according to claim 1, in which the casing is formed of drawn or extruded profiledsection material, and is cut from a profiled bar.

3. A machine according to claim 1 or 2, in which the dimensions of the core hole of the casing are such that the stator is interlockingly retained in the casing.

4. A machine according to any preceding claim, in which radially symmetrically arranged core holes are formed about the perimeter of the casing and a corresponding number of boreholes are also radially symmetrically arranged in the end shields to receive fastening means by which the end shields are attached to the casing.

5. A machine according to claim 4, in which the casing has a polygonal radially symmetrical crosssectional configuration and the end shields have a similar polygonal radially symmetrical configuration, the boreholes to receive the fastening means being arranged in the corners of the polygon.

6. A machine according to claim 5, in which the polygons are hexagons.

7. A machine according to claim 4,5 or 6, in which the boreholes formed in the casing to receive the fastening means being formed as slots.

8. A machine according to any of claims 4 to 7, in which abutment bosses are formed inside the casing and provide abutment surfaces for at least one of the end shields.

9. A machine according to any preceding claim, in which the bracing arm is also a constituent element of the machine casing.

10. A machine according to claim 9, in which the pivot arm and the bracing arm are arranged on diametrically opposite sides of the casing.

11. A machine according to claim 5 or 6, in which the bracing arm is offset, relative to the pivot arm by at least one division between the bores and the boreholes.

12. An electrical machine as claimed in any preceding claim which is a vehicle alternator.

13. An electrical machine constructed substantially as herein described with reference to and as illustrated in the drawings.