EP1111734B1 - Moulded flat commutator - Google Patents

Abstract

The laminations (12) are held axis-symmetrical to a collector axis in a compressed insulation of a collector body. Each lamination forms with a surface a part of a concentric brush slide path (18), along which the laminations are separated by insulating columns (14). The lamination surfaces are lowered along the slide path, at least at one side, towards the insulating columns. The lamination surfaces are lowered as inclines down to the insulating columns.

Description

The invention relates to a commutator-coal brush combination according to the preamble of claim 1.

Such a combination is for example from the document DE-PS 955 072 known.

Commutators, in particular as large-series products for universal motors in AC operation, have experienced a steady development to higher electrical outputs, higher speeds and longer service lives, as the requirements for the collector special product - with simultaneous pressure on prices - have steadily increased with technical progress. However, advances of this kind can be devalued by the fact that other components of electric motors do not keep up with the development and thus limit the performance or service life of the engine. This is especially true for carbon brushes, which are to be used in conjunction with the commutator and thereby regularly the weaker, i. give off susceptible limb.

In this case, carbon brushes have also been further developed in terms of electrical performance and mechanical strength and stability, on the one hand occurring during commutation on a carbon brush between two simultaneously contacted commutator short-circuit currents by higher set contact resistance - at the same time as high current carrying capacity - were given, for the brushes have been divided into two or three layers (stratified carbons), between which the contact resistances are to be kept as high as possible. Nevertheless, at the carbon brushes during slow, in particular also reversing operation, such as in washing machines, large power losses occur, in particular in the respective initial phase of operation, and strong ones Burns on the carbon brushes on. Furthermore, the carbon brushes are worn, especially at high speeds by "brush fire", wherein the erosion of the carbon brushes and also partially deposits the copper fins in the insulating gaps between the copper fins and causes the risk of short circuits.

According to the prior art according to the CH 109 189 A has already been provided to save the copper fins on the periphery of mica insulated power reversers, on the one hand to achieve greater distances between the slats and thus to increase the creepage path between the slats and to create a receiving space for contamination. At the same time, however, losses of mechanical strength of the commutator should not occur, such as with narrower slats and larger circumferential widths of insulating material, or the conductor cross-sections of the slats should be greatly reduced.

With a change in the insulating gaps u.a. also the formation of brush fires can be reduced. However, this can not be achieved solely with a change to the lamellae and gaps, without involving the carbon brush in each case.

According to the invention is now from the collector side with a view to the interaction of collector and carbon brushes a significant improvement in Kommutatoreigenschaften total including the carbon brushes in particular with a view to reducing the power losses and the carbon brush wear with a commutator carbon brush combination according to the claim 1 scored.

By partially lowering the fin surface to the Isolierspalten can be achieved with a given basic design of commutator and carbon brush effectively lower coverage, i.e., reduce the support of the carbon brush in the circumferential direction in proportion to the parting of the commutator. This reduces the especially brush-eating short-circuit currents, especially in AC-powered motors. At the same time, such reductions are suitable for reducing brush firing at high speeds and also for shifting the corresponding flashovers out of the critical area of the lamella edges and the insulating gaps. The copper lamellae are little eroded and, which is still the case of brush firing to burn, found next to the insulating gaps still receiving space in the region of the subsidence.

It has been found that, in this way, especially the high power requirement at the beginning of the slow reversing operation, for example in washing machines, is reduced. The corresponding services were incurred as power losses, which were reflected in the carbon brushes with appropriate wear, so that now in this area a low-wear operation is achieved. In addition or in addition, with such a reduction, a copper and carbon wear in general and especially at high speeds to reduce. At the same time, this opens up the possibility of switching from the elaborate layered carbon brushes, at least less critical cases, to simpler, integral carbon brushes.

In the DE-PS 955 072 It is described that the edges of the there called Wenderstege slats are broken in order to complicate a beard on the web material.

Also concerned with the design of commutators in miniature motors DE-43 39 981 A1 , which provides Kantenabschrägungen the Rohkommutator, is exhausted in the narrower edge design, which is to avoid burrs during finishing. In this regard, an outer diameter portion of the commutator, which is excessively provided for final twisting, is provided with a slope at one or both of the blade edges. However, this bevel is largely removed during turning, so that suitably remain after turning at most small residual inclined surfaces at the edges. This design is exhausted in the avoidance of errors by the twisting and should only lead to a flawless lamella shape.

Fig. 1

Kommutatorlamellen und Kohlebürste bei einer herkömmlichen Ausführungsform,

Fig. 2

Kommutatorlamellen und Kohlebürste bei einem Kommutator gemäß einer ersten Ausführungsform der Erfindung (Abwicklung),

Fig. 3

Kommutatorlamellen (vergrößert) bei der Ausführungsform gemäß Fig. 2 (Abwicklung),

Fig. 4

eine abgewandelte (zweite) Ausführungsform von Kommutatorlamellen (Abwicklung),

Fig. 5

Form und Anordnung von Kommutatorlamellen bei einer dritten Ausführungsform und

Fig. 6

Teilansicht der Kommutatorlamellen gemäß Fig. 5 (Abwicklung) und Kohlebürste dazu.

In addition to an example of a conventional embodiment of commutator or commutator blades with respect to a carbon brush, several embodiments of the subject invention are shown in the drawing and are described in more detail below. In the drawing show in each case simplified contoured form and in each case in paraxial view or partial view

Fig. 1

Commutator bars and carbon brush in a conventional embodiment,

Fig. 2

Commutator and carbon brush in a commutator according to a first embodiment of the invention (development),

Fig. 3

Commutator bars (enlarged) in the embodiment according to FIG. 2 (unwinding),

Fig. 4

a modified (second) embodiment of commutator bars (unwinding),

Fig. 5

Form and arrangement of commutator bars in a third embodiment and

Fig. 6

Partial view of the commutator bars according to FIG. 5 (unwinding) and carbon brush.

In Fig. 1, individual fins 1 of a commutator are illustrated with its cross-section or outline, as it is conventionally formed and arranged to a carbon brush 2, the two layers 3.4 with an electrically not conductive, in any case, high-resistance intermediate layer 5 is formed. The carbon brush is made obliquely against a indicated by an arrow 6 main running direction, but this is only a known measure against the risk of jamming in a (not shown) brush holder. The brush 2 is pressed in a known manner by spring pressure or the like. Against the surfaces of the commutator bars 1 and nachgeschoben in full-surface wear of the carbon brush 2.

However, it has hitherto been shown that the wear of the carbon brush 2 is not uniform, as one might assume, for example, in a purely mechanical grinding.

At high speeds, inductive residual stresses resulting from armature windings, which are electrically connected to the slats 1, with corresponding Abreißfunken ("brush firing") in the direction of rotation behind edges 7 and 8 of carbon brush 2 and slats 1 with spark erosion and material deformation both at Brush 2 as well as on the copper lamella 1. Particularly dangerous is that the material then deposited in insulating gaps 9 between the slats 1 and the lamellae short-circuit each other.

Another form of carbon brush stress arises in particular in reversing operation and certainly at reduced speeds. There are ablation regions 10, 11 on the carbon brush, which infiltrate both layers of the outer sides of the contact surfaces and reduce the contact areas in the circumferential direction. This is evidently due to short-circuit currents, since even with subdivision of the carbon brush 2 into layers 3 and 4, each layer conceals adjacent lamellae simultaneously during the rotation of the lamellae 1 and maintains contact with both. The electrical power losses are significantly higher in such a constellation, especially at the beginning of a reversing operation, the power loss is significantly in the destruction of coal in the areas 10 and 11 and only later becomes smaller, if only a portion of the coal for contacting the slats to Available.

FIG. 2 now shows collector lamellae 12 (in the form of a straight elongated development mold) in juxtaposition to a layered carbon brush 13, wherein the surfaces of the lamellae 12 are lowered towards intermediate insulating gaps 14 with oblique edge surfaces 15. This results from the juxtaposition (here, for example, only vertically employed) coated carbon brush 13 with coal layers 16 and 17 that these coal layers 16,17 find a grinding path 18 from the remaining surfaces of the fins 12, in which they contact at least predominantly via a blade 12 with one of the coal layers 16 or 17. On the other hand, however, the layered carbon brush 13 is maintained in its width, which is technically difficult to change and thus receives a wide circulation on the slideway 18, usually on two fins 12, so that the coal is not as on a " Moguls slope "flutters.

It is understood that the lowering of the lamellar surfaces created here by sloping surfaces 15 can basically also be stepped, however, the oblique shape over a stepped shape has the advantage of mechanically softer transitions for greater smoothness of coal and ease of manufacture in view of the small slat width usually less than or equal to 3 mm. The transition edges are appropriately rounded.

Another particular advantage of the oblique edge surfaces 15 lies in the fact that the brush firing with its separating spark on the side of the copper passes immediately on the inclined surfaces and these, uncritical lying outside of the grinding path 18 areas are relatively robust. In any case, however, eroded material finds a lot of space in the insulating gaps which are opened and widened with the depressions, so that fillings, bridging and the associated short circuits are largely ruled out.

The width of the copper lamellae as a whole has been maintained, even though the surface used for the grinding lane 18 has been reduced. This has advantages over a reduction of the lamella width certainly advantages in terms of the available copper mass against mechanical and thermal stresses as well as with respect to the electrical line with corresponding cross-sections.

Compared to the enlarged in Fig. 3 reproduced fins 12 with a symmetrical configuration, Fig. 4 shows one of many case by case advantageous variants with slats 19 with asymmetric design, with an obliquely lowered edge surface 20 is much larger than one on the other side lowered edge surface 21 and also for a slideway 22 only a relatively narrow median strip left. Such cross-sectional designs take particular account of the predominant directions of rotation consideration. In the simplest case, it may be sufficient to provide only a one-sided lowering, in particular bevel, in order to catch especially the brush fire with such a lowering of the edge at a fixed predetermined direction of rotation. In both cases, angles between the lowered inclined surfaces are below 50 ° (or as an obtuse angle calculated over 130 °), resulting in relatively large inclined surfaces. The contact areas remaining for the grinding path are narrower as the intermediate areas of inclined surfaces and insulating gaps.

Fig. 5 shows the copper fins 23 of another collector in its cross-sectional contour, which is shown enlarged in Fig. 6 as a development. In both cases, the commutator cohesive insulating compound is not shown, which leaves in any case between the fins 23 still insulating gaps.

The fins 23 have relatively large lowered sloping surfaces 24 with a relatively low inclination relative to a central strip for a grinding path 25. A currently drawn in a transition position between two slats 23 carbon brush 26 contacts at most in a very short moment both slats 23 so that short-circuit currents are negligible, but at the same time a mechanical continuous support on the slideway 25, formed by the respective outer central strip of the slats 23 between the subsidence, is guaranteed. In this case, a monolayer carbon brush 26 can be provided even with advantage for the production cost and the size of the coal. This is especially true when provided for a low-backlash storage of coal 26.

Claims (5)

1. Commutator and carbon brush combination for an electric motor, having commutator bars (12, 19, 23) made of copper or a similar electrically conductive material, which bars (12, 19, 23) are held in insulation belonging to a commutator body In axial symmetry to an axis of the commutator and each form, at a surface, part of a concentric slide track (18, 22, 25) for carbon brushes (13, 26), around which slide track the bars (12, 19, 23) are separated from one another by interstices which each have, in an outer region facing towards the slide track (18, 22, 25) for brushes, a gap in insulation (14) free of insulating material and, in a deeper region facing towards the axis of the commutator, insulation which forms a boundary of the gap in insulation, the surfaces of the bars (12, 19, 23) each having on at least one side, around the slide track (18, 22, 25), regions (15, 20, 21, 24) which are lowered towards the gaps in insulation, characterised in that the lowered regions on the bars are of a size such, in relation to the carbon brushes, that, although continuous support is still ensured for the carbon brushes on the slide track as they cross between two bars, they contact the two adjacent bars by one layer of carbon at most very briefly, and in that the commutator is in the form of a moulded commutator having moulded insulation.
2. Commutator according to claim 1, characterised in that the surfaces of the bars (12, 19, 23) are lowered in the form of edge faces (15, 20, 21, 24) which slope down obliquely to the gaps in insulation,
3. Commutator according to one of claims 1 to 4, characterised in that the edge faces (15, 20, 21, 24) which slope down obliquely make an angle of less than 50° with the slide track.
4. Commutator according to one of claims 1 to 3, characterised in that the lowered regions have edges which are rounded in relation to the contacting regions of the slide track (18, 22, 25).
5. Commutator according to one of claims 1 to 4, characterised in that the contacting regions (18, 22, 25) of the bars (12, 19, 23) are narrower than the width, added together if required, of the lowered regions.

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