GB2033674A

GB2033674A - Electrical machine: securing end shields

Info

Publication number: GB2033674A
Application number: GB7936277A
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: JPS5556440A; DE2845668A1; FR2439497A1

Abstract

Locating projections (44) are formed on at least one end shield (13) of the housing of an electrical machine by means of a stamping process. These projections fit in locating apertures in a casing portion of the housing so that the bearing supported in a central boss (18) of the end shield is accurately centered. The projections are stamped out after the end shield has been placed in its final position on the casing so that the projections are pressed into the locating apertures as they are formed. Such a machine is suitable as an alternator for motor vehicles. <IMAGE>

Description

SPECIFICATION Electrical machine The invention relates to electrical machines.

In known electrical machines, the or each end shield is conventionally centrally located, relative to the machine casing, by means of a locating spigot and groove. In order to produce the locating spigot and groove, an expensive machining process is necessary. Moreover, the locating spigots and grooves exhibit undesirable play due to manufacturing tolerances.

An electrical machine, according to the present invention, has a housing comprising a casing portion and at least one end shield, a machine shaft, and a bearing in the end shield for the machine shaft, such bearing being centrally located by the respective end shield by projections on the end shield engaging in corresponding apertures in the casing portion of the housing.

This has the advantage that centering can more easily be made free from play. Moreover, the centering means can be produced without a machining operation, and therefore economically.

It is particularly advantageous for central location of the end shield on the casing portion of the housing, and attachment of the end shield to the casing portion, are effected by different, independent means. Centering itself may be effected with the aid of a simple tool. Particularly advantageous is the fact that, once achieved, the central location is maintained, even if the machine is subjected to severe stresses, and the end shield is removed, for example, for purposes of repair.

The invention includes a method for the central location of an end shield of an electrical machine on a casing portion of the machine housing, in which the screws for securing the end shield are inserted through bores in the end shield and into boreholes in the casing portion and are looselytigthened and the end shield which is to be centrally located, and the casing portion are presented to each other in the desired central position, and in which, by means of a stamping process, projections are formed on the end shield and are pressed into further boreholes in the casing portion, and the screws are secu rely tightened.

The invention is further described, by way of example with reference to the drawings, in which Figure lisa partially sectioned generalarrangement drawing of an alternator, Figure 2 is a cross-section of the casing portion of the machine housing, Figure 3 is an elevation of an end shield of the alternator, and Figure 4 is a section of the end shield.

The alternator shown in Figure 1 has a machine housing comprising a housing shell 11, a first end shield 12, and a second end shield 13. On the housing shell 11 there is formed a pivot arm 14, and on the first end shield there is formed a bracing arm 15.

In a first bearing boss 16 in the first end shield 12 there is arranged a first bearing 17, and in a second bearing boss 18 there is arranged a second bearing 19. The housing shell 11 serves as a casing portion of the housing and receives a stator 21, having a stator winding 22, to which a rectifier unit 23, which is mounted on the second end shield 13, is serially connected. A machine shaft 24 is journalled by the bearings 17, 19 and carries a rotor, with a core 25, pole wheels 26, and an excitation winding 27. The ends of the excitation winding 27 are connected to slip rings 28, which are also mounted on the machine shaft 24. A module comprising a voltage regulator 29 and a brush holder31 is operatively associated with the slip rings 28. Afan impeller 32 and a belt pulley 33 are also clamped on the machine shaft 24 by means of a nut 34.Apertures 35 in the first end shield 12, and apertures 36 in the second end shield 13, serve for ventilation of the machine.

Figure 2 shows the pivot arm 14 formed on the housing shell 11. Boreholes 37, which serve for attachment of the second end shield 13, are also provided in the housing shell 11. The stator 21 is inserted between the inner shoulders 38. If pressure is used to insert the stator 21, it is thereby at the same time clamped in the housing shell 11.

The end-elevational view of the second end shield 13 of Figure 3 shows the apertures 36 for ventilation of the machine, and boreholes 39 for attachment of the second end shield 13 to the housing shell 11, and also the bearing bush 18. For reinforcement of the second end shield 13, the rims 41 of the apertures 36 are flanged. Apertures 42, for diodes of the rectifier unit 23, are also provided in the second end shield 13. Lastly, two indentations 43 are visible; these are shown in further detail, however, in Figure 4.

Figure 4 is a side-elevational view of the second end shield 13 but is shown sectioned in the region of the indentations 43. It is evident that, as a result of the stamping on one side, projections 44 are created on the opposite side.

With hitherto existing methods for the central location of an end shield relative to the housing shell, as already mentioned, locating spigots and grooves or recesses are formed in the components which are to be centered. In the electrical machine according to the present invention, on the other hand, centering is performed in the course of assembly of the machine. In the electrical machine of the drawings, first of all four screws, which are not shown in the drawing, are inserted in four opposite boreholes 39 in the second end shield 13, and in the boreholes 37 of the housing shell 11. The end shield 13 is then loosely attached to the housing shell 11 by means of the screws. In the next stage of assembly, the bearing boss 18 is centrally located relative to the housing shell 11. Next, the end shield 13 is accurately centered or located in its desired position on the housing shell 11. By means of a stamping process the two indentations 43 are formed in the end shield 13 so as to overlie the two remaining boreholes 37 in the housing shell 11. The material of the end shield 13 is thereby caused to flow, in the form of locating projections 44, into the boreholes 37 serving as locating apertures in the housing shell 11. By this means, the end shield 13 is permanently centered in the housing shell 11. Lastly, the four screws are firmly tightened, and the end shield 13 is thereby clamped to the housing shell 11.

It is also possible, of course, to center and clamp the first end shield 12 in a like manner on the housins shell 11.

Claims

1. An electrical machine having a housing comprising a casing portion and at least one end shield, a machine shaft, and a bearing in the end shield for the machine shaft, such bearings being centrally located by the respective end shield by projections on the end shield engaging in corresponding apertures in the casing portion of the housing.

2. A machine according to claim 1, in which the projections are formed by indentations on the opposite side of the end shield.

3. A machine according to claim 1 or 2, in which the locating apertures are formed by boreholes in the casing portion of the housing.

4. A machine according to any preceding claim, in which the end shield is provided additionally with bores and is attached to the casing portion of the housing by means of fasteners which pass through such bores and enter boreholes in the casing portion of the housing.

5. A machine according to any preceding claim, in which the housing of the machine comprises a housing shell and two end shields and in which both end shields are centrally located in the housing shell (which forms the casing portion) by means of projections on the end shields and apertures in the housing shell.

6. A method for the central location of an end shield of an electrical machine on a casing portion of the machine housing, in which the screws for securing the end shield are inserted through bores in the end shield and into boreholes in the casing portion and are loosely tightened and the end shield which is to be centrally located, and the casing portion are presented to each other in the desired central position, and in which, by means of a stamping process, projections are formed on the end shield and are pressed into further boreholes in the casing portion, and the screws are securely tightened.

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

8. A method of locating an end shield on a casing portion of a housing of a electrical machine, substantially as herein described with reference to the drawings.