GB2234020A

GB2234020A - Alternating-current generator bearings

Info

Publication number: GB2234020A
Application number: GB9015490A
Authority: GB
Inventors: Henning Fasterding; Karl-Heinz Koplin; Norbert Philipp
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1989-07-14
Filing date: 1990-07-13
Publication date: 1991-01-23
Anticipated expiration: 2010-07-13
Also published as: IT9020891A1; IT1244302B; FR2649839A1; JPH0352534A; GB2234020B; FR2649839B1; DE3923272A1; GB9015490D0; IT9020891A0

Abstract

In an alternating-current generator, at least one of the bearings of the rotor shaft comprises an outer race (12a) provided with axial longitudinal grooves (13). The bearing is inserted into a bearing plate fitting recess (11) and hub material is pressed into the axial grooves in order to prevent rotation of the race whilst simultaneously allowing axial movement for thermal expansion. The material can be compressed by peening-over hub material from the bearing plate (10) into the grooves, or by turning at least one eccentric pin (16), which is seated in an axial bore (17) adjacent to the bearing plate fitting recess (11). <IMAGE>

Description

DESCRIPTION AN ALTERNATING-CURRENT GENERATOR

The present invention relates to an alternating-current generator, and in particular, but not exclusively, to a three-phase generator, as an alternator for mobile units, motor vehicles and the like.

It is known (DE-OS 27 14 102) to mount the rotor shaft on both ends in ball bearings which are held by fitting recesses in a pair of bearing plates (so-called bearing plate A on the drive side and bearing plate B on the brush side) which normally form the housing of the three-phase generator. The ball bearing is disposed at least on one side of the threephase generator, in the hub of bearing plate B which holds it, with the interposition of a constructional part, which surrounds the bearing in a dish-like manner in such a way that, in addition to sealing the bearing, two felt rings, which are seated on the rotor shaft, are held and accommodated.

Instead of making the constructional part surrounding the outer race of the ball bearing from metal, it is also known to provide a fitting ring for the bearing which is made of plastics material, which is seated-in the form of a pot in the hub of the respective bearing plate and which holds the N -2ball bearing inside it in such a way as to prevent it rotating, or to provide an O-ring in this region. These elements are necessary in the previous bearings because the ball bearing B should at least have a sliding seat or push fit on the outer race relative to the bearing plate fitting recess in order to ensure longitudinal compensation for tolerances and thermal expansion, but at the same time must be seated so firmly in the fitting recess that the outer race does not rotate.

For this reason, previous solutions have had problems to the extent that an additional fitting ring is always required, which not only increases costs, but also prevents optimum heat dissipation because the heat arising in the bearing cannot readily dissiptate through the plastics material of the fitting ring.

It is thus one object of the invention to design the ball bearings for the rotor shaft in three-phase generators especially when used as alternators for motor vehicles and the like, and especially the ball bearing B in the bearing plate B of the generator in such a way that on the one hand the push-fit character is retained with respect for the axial longitudinal compensation and the bearing is satisfactorily prevented from rotating, and, on the other hand, heat dissipation is improved.

T In accordance with the present invention an alternating-current generator is provided having a stator core of lamination stack and a rotor rotating therein, whose shaft rotates in bearings seated on both sides in bearing plate fitting recesses of bearing plates forming the housing, wherein the outer race of the bearing provided with axial longitudinal grooves is fitted directly into the fitting recess of at least one bearing plate holding the bearing and is prevented from rotating in the hub by the displacement of hub material inwards into the longitudinal grooves of the outer race whilst retaining its push-fit character.

This has the advantage that, by directly fitting the outer race of the ball bearing in a sliding seat into the bearing plate, optimum heat dissipation (metal on metal) is achieved, while, on the other hand, frictional prevention of rotation is ensured by the groove effect in the form of the outer race of the ball bearing, which is achieved by peeningover hub material into the grooves of the ball bearing outer race.

Omitting separate, previously required fitting rings not only reduces costs, but also makes more precise the necessarily concentric seat of the ball bearing and hence the rotor shaft to the stator core or stack, which in turn is received by fitting recesses in the two bearing plates.

In order to achieve means for permanent prevention of rotation, it is particularly advantageous that, during peening-over, material from the hub region of the bearing plate is pressed into the grooves on the outer race of the ball bearing, as a result of which longitudinal compensation is clearly maintained and/or to press hub material, which is adjacent elsewhere, into the grooves in a locally limited manner, for example by means of an eccentric pin seated in a hub bore.

Specific embodiments of the present invention are described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a side view through one embodiment of the generator in accordance with the present invention, illustrating a partial fragmentary view of the bearing B for the rotor shaft; Fig. 2 is a schematic plan view of the special form of a ball bearing to be used in accordance with the present invention having grooves in the outer race; and Fig. 3 is a schematic plan view of the hub region of bearing plate B having a ball bearing inserted which is secured by peening-over hub material.

p j L.1 A ball bearing, which has axial grooves in its outer race, is directly fitted in a "metal-to-metal transition" into a fitting recess of the bearing plate B of a three-phase generator, so that an axial tolerance similar to that of a sliding seat is obtained, and, in order to secure the ball bearing in the hub, to peen it over in such a way that hub material presses into the grooves.

In Fig. 1, bearing plate B, which is shown in partial fragment only, is designated 10 and the fitting recess formed by the hub region 10a of the bearing plate 10 of the three-phase generator for the ball bearing is designated 11. The ball bearing 12 is held by the fitting recess 11 directly in the metal/metal transition and, as shown in Fig. 2, its outer race 12a has axial longitudinal grooves 13 which form a kind of toothing, but which are preferably formed in such a way that the outer race 12a of the ball bearing 12 is inserted into the fitting recess 11 holding it in such a "loose" manner that it is not held in a force fit, but rather that a push-fit character is obtained for the bearing of the ball bearing 12.

To this end, the groove formation 13 in the outer race 12a is such that outwardly pointing tips of the toothing are not formed, but rather there are only axial grooves in the outer race which are inwards at a -6greater distance to one another, so that table-shaped or mesa-shaped flat elevations are formed between these grooves, their surface simulating the outer periphery of the outer race of the ball bearing.

The ball bearing, which is push-fit in the bearing plate, is actually secured by a peening-over operation in which hub material is pressed into the grooves on the outer race of the ball bearing by the bearing plate.

In the embodiment shown (see Fig. 3), four slots 14, which are uniformly distributed about the periphery, are formed in the hub 10a of the bering plate B by the peening-over action, and the material located between these slots and the outer race of the ball bearing, as a result of this slot formation, is pressed in the form of a thin layer 15 of material onto the outer race in such a way that said material also gets into the grooves 13 of the outer race of the ball bearing. As a result, any possible rotation of the ball bearing is reliably prevented by this frictional penetration and hooking or engagement, while on the other hand longitudinal compensation of the bearing in the axial direction is maintained, since the grooves 13 can naturally slide along the pressed-in peened-over material together with the ball bearing.

1 It can be seen from the enlarged representation in Fig. 2 of the groove formation on the outer race of the ball bearing that the majority of the outer surface of the ball bearing is maintained, wherein the groove formation takes up for example only approximately 25 to 30% of the outer race surface of the ball bearing if numerical values are to be used for the purpose of better understanding, although these numerical values do not restrict the present invention to these ranges. In other words, the metal/metal contact between the inner surface of the hub of the bearing plate B and the outer race of the ball bearing is maintained to a high degree of optimum heat dissipation, so that a doubly improved effect is achieved over the use of conventional plastic fitting rings, namely frictional prevention of rotation of the ball bearing and satisfactory direct heat transfer.

Furthermore, it is also possible to insert an eccentric pin 16 into a bore 17 at any point in the hub of the respective bearing plate holding he ball bearing, wherein the remaining material thickness A between the bore 17 and the bearing plate fitting recess 11 may only be small. By turning the eccentric pin 16, the intermediate hub material in region 15a is also pressed almost along the entire axial length of the ball bearing at this point into the longitudinal -8grooves on the outer race of the ball bearing, thus producing an additional or even a sole means of prevention of rotation, that is, the peening-over could be dispensed with.

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Claims

1. An alternating-current generator is provided having a stator core of lamination stack and a rotor rotating therein, whose shaft rotates in bearings seated on both sides in bearing plate fitting recesses of bearing plates forming the housing, wherein the outer race of the bearing is provided with axial longitudinal grooves fitted directly into the fitting recess of at least one bearing plate holding the bearing and is prevented from rotating in the hub by the displacement of hub material inwards into the longitudinal grooves of the outer race whilst retaining its push-fit character.

2. An alternating-current generator as claimed in claim 1, wherein the outer race of the bearing is peened-over in the hub holding it.

3. An alternating-current generator as claimed in claim 2, wherein, during peening-over, material of the bearing plate hub which holds the bearing is pressed into the grooves on the outer race of the ball bearing.

4. An alternating-current generator as claimed in claim 2 or 3, wherein, for peening-over, a plurality of slots, which are distributed uniformly about the hub periphery, are formed in the hub, wherein the material between the slots and the outer race of the bearing penetrates frictionally into the grooves of the bearing outer race.

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5. An alternating-current generator as claimed in any of the preceding claims, wherein, in the hub region of the bearing plate holding the bearing, one or more bores each receiving an eccentric pin are disposed adjacent to the fitting recesses of the hub in such a way that, by turning the eccentric pins, hub material between the or each bore and the ball bearing outer race is pressed over a long axial region of the hub into the axial grooves of the ball bearing outer race, whilst the axial sliding seat character is retained.

6. An alternating-current generator as claimed in any of the preceding claims, wherein the bearings comprise ball bearings.

7. An alternating current generator substantially as hereinbefore described. with reference to, and as illustrated in, the accompanying drawings.

. Published 1991 atIbe Patent Office. State House. 66/71 High Holborn. London WCIR47?. Further copies maybe obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray, Kent.

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