GB2328561A

GB2328561A - Plastic cap, having an expansion notch, for the slip-ring chamber of electric machines.

Info

Publication number: GB2328561A
Application number: GB9816891A
Authority: GB
Inventors: Hermann Trinks; Peter Skala
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-08-09
Filing date: 1998-08-03
Publication date: 1999-02-24
Anticipated expiration: 2018-08-03
Also published as: ES2151412B1; ITMI981638A1; GB2328561B; DE29714276U1; FR2769147B1; ES2151412A1; ITMI981638A0; FR2769147A1; GB9816891D0

Abstract

A plastic cap 39 for a slip ring arrangement (fig. 1, nos.28,29) of an electric machine, such as a three phase generator for motor vehicles. The plastic cap 39, which is fitted non-rotatably in the bearing bore of the housing shell 12, is pot shaped and encloses the slip-ring arrangement (fig.1, nos.28,29) to prevent the penetration of water into the area(fig 1, no.38). The inner portion plastic sleeve of the cap acts as a bearing gauge ring 43 and has one or more expansion notches 46 which are sinuous (or curved) 46 (and fig.5, no.46A) in profile wherein the notch bridging material 48 is thinner that of the surrounding wall area. The expansion notch acts to accommodate and compensate for the different rates of thermal expansion of the bearing, the housing and the plastic sleeve.

Description

2328561 1 Electrical machine. in particular a e-jphase generator for

vehicles

Background art

The invention proceeds from an electrical machine, in particular a threephase generator for vehicles having a claw-pole armature according to the preamble of the main claim. From DE-GM 9107 542 a three-phase generator for vehicles is already known, which has a claw-pole armature, the excitation winding of which is supplied by means of carbon brushes via an enclosed slipring arrangement. The enclosure of the slipring area is effected in said case by means of a plastic sleeve having an end portion designed as a gauge ring, which is inserted between the bearing at the shpring side and the bearing bore. The plastic sleeve embracing the shpring area is provided there with an opening for receiving the brush holder. In order to prevent the plastic material from being permanently squeezed together in the event of thermal expansion of the bearing and the bearing bore, a longitudinal groove - a so-called expansion notch - is formed there. The latter effects an expansion of the gauge ring and at the same time prevents penetration of water into the slipring area. Experience has shown however that said expansion notch in the form of a longitudinal groove still does not work properly because the remaining web at the groove base is so stiff that a radial expansion of the bearing and a resultant reduction in the wall thickness of the gauge nnlkjs insufficient and leads to overloading of the bearing.

Advantages of the invention In contrast, the three-phase generator for vehicles according to the invention having the characterizing features of the main claim has the advantage of enabling a far better expansion at the periphery of the gauge ring, which expansion reliably 2 prevents penetration of water into the slipring area. It is particularly advantageous to provide the expansion notch at a plurality of points on the sleeve.

Further advantages of the invention are evident from the following description, the sub-claims and the drawings.

Drawings Figure 1 shows a longitudinal section through a three-phase generator having a slipring-enclosing plastic sleeve with a bearing gauge ring, Figure 2 a side view of the sleeve, Figure 3 a plan view of the sleeve in the direction of the arrow P, Figures 4 and 5 show embodiments of the expansion notch to an enlarged scale, Figure 6 an expansion notch according to prior art, Figure 7 a partial section through the plastic sleeve according to Figures 4 and 5.

Description of the embodiment

The three-phase generator for motor vehicles, which is shown 'm longitudinal section m Figure 1, substantially comprises a stator 10 in the form of a lannnated core, which carries a three-phase stator winding 11 and to which two housing shells 12 and 13 are fastened by means of screws 14. The housing shells 12, 13) form end shields 15, 16, m which at the drive side a relatively large drive bearing 17 and at the brush side a weaker slipring bearing, 18 is inserted. Disposed rotatably Mi the stator 10 is a claw-pole rotor 19, which comprises two claw-pole discs 20, 21 and a flux-directing piece 22 clamped between them, on which an excitation Winding 23 is mounted. The claw-pole rotor 19 is pressed onto a rotor shaft 24, which is accommodated in the two beafings 17 and 18 and has at the 3 drive-side end a threaded projection 25 for the purpose of fastening a driving pulley.

A fan disc 26, 27 for dissipating the heat loss of the three-phase generator is fastened on the rotor shaft 24 on either side of the clawpole rotor 19. Provided at the brush-side end of the rotor shaft 24 is a slipring arrangement comprising two slip rings 28, 29, which lie adjacent to one another with clearance and are fastened on the rotor shaft 24 so as to be insulated from the latter and from one another. They are connected by conductors (not shown), which are run in an insulated manner in the rotor shaft 24, to connections ' W which, for supplying power to the excitation winding, are contacted by the latter's line ends 3 1. A rectifier unit 32 (not shown mi detail) is fastened. by screws 33' and, moreover, a brush holder 3 4 with the carbon brushes for the sliphings 28, 29 as well as a voltage regulator 35 are fitted and wired up on the outside of the end shield 16 of the brush-side housing shell 13. Said unit 32 is finally additionally enclosed by a pot-shaped cap 3 W which is likewise fastened to the brush-side housing shell 13 and accommodates the electrical connections 37 of the generator.

For moisture- and dirt-proof enclosure of the slipring area 38 a plastic sleeve 39 is provided, which is illustrated in Figures 1 to 3 and has an opening 40 for receiving the brush holder 34, which opening is sealed off in an outward direction by a sealing ring 41 at the bottom end of the brush holder 34.

The plastic sleeve 39 is closed at its outer end by means of a base 39A and therefore surrounds the sliprings 28, 29, which are disposed behind the slipring bearing 18 on the free end of the rotor shaft 24, in a potlike manner.

4 The bearing-side end 339B of the plastic sleeve 3 9 forms a bearing gauge ring 43 3, which is fitted non-rotatably mi the bearing bore of the housing shell 12 by means of at least one shoulder 45 and accommodates the outer ring of the slipring bearing 18. The gauge ring 43 allows the bearing 18 to move a ally and prevents c xl deflection of the bearing seat. Because plastic material expands differently to metal, there are formed at the outer periphery of the bearing gauge ring one or more axially extending expansion notches 46, 46A, which enable the expansion at the periphery of the gauge ring and yet prevent the penetration of water into the slipring area 38. The expansion notches are shown to an enlarged scale 'm Figures 4 and 5; they moreover enable breathing and replace the special recesses which were previously required. A radially outwardly directed annular collar 47 injection-moulded on the end of the gauge ring 43 closes off the expansion notch(es) in forward direction.

The expansion notches according to the invention comprise a web 48 having a more or less extremely undulating profile. The webs 48 are at said points much thinner than the remaining wall. A construction according to Figure 4 with an extreme undulation 46 would be the ideal state but is difficult to manufacture. For said reason, a less extreme undulation 46A or notch according to Figure 5 has proved successful. The detail accordmig to Figure 6 shows an expansion notch according to prior art which, however, has not proved particularly effective.

The idea accordin. to the invention may be used in all electrical machines, i.e.

to also motors, having an identical or similar slipring arrangement.

Claims

1.

Electrical machine, in particular a three-phase generator for vehicles having a claw-pole armature, the excitation winding of which is supplied by means of carbon brushes via an enclosed slipring arrangement, wherein the enclosure of the slipring area is effected by means of a plastic sleeve, which is fitted on a housing shell for an armature bearing and has a sealed opening for receiving a brush holder and is closed at its outer end so as in a pot-like manner to surround the sliprings disposed behind the slipring bearing on the free end of the rotor shaft and is designed at its inner end as a bearing gauge ring, which is insertable non-rotatably into the bearing bore of the housing shell and accommodates the outer ring of the bearing, and wherein the end of the plastic sleeve designed as a bearing gauge ring has at least one expansion notch, which extends over the bearing width and is closed in forward direction by a material bridge of the plastic sleeve, characterized in that the remaining web (48) of the expansion notch (46, 46A) has a sinuous profile and is thinner than the surrounding area.

2. Machine according to claim 1, characterized in that the web profile is meander-like.

J.

4.

Machine according to claim 1, characterized in that the web profile is curved.

An electric machine substantially as herein described with reference to Figures 1 to 4 and 7.

(J0

5.

An electric machine substantially as herein described with reference to Figures 1 to -3), 5 and 7.