EP0054727B1 - Commutator and method of manufacturing the same - Google Patents

Description

The invention relates to a commutator with a reinforced segment assembly, which is arranged with the interposition of insulation on a hub or an armature shaft, and to a method for producing such a commutator.

The known commutators with an armored segment assembly are those of the arch pressure type. With them, so-called segment jumps can be avoided even at high centrifugal stresses, as occurs at high speeds, because the arch pressure can be chosen so large that the surface pressure generated by the arch pressure between the segments and the insulating lamellae is sufficient for all operating conditions Reliably prevent emigration of the segments. However, commutators are often not only exposed to large flow forces, but also to high thermal stresses. The deformation of the brush running surface that occurs as a result of the heating of the commutator, which is a reversible deformation in the form of short- and / or long-wave deviations from the cylindrical shape, then limits the maximum speed for which the commutator can still be used.

In order to be able to suppress these deformations by means of an even higher arch pressure, it was proposed (DE-A 2 132 928) not only to increase the cross-section of the reinforcement rings even further, but this is only possible if the reinforcement rings are placed on the outer surface of the segmental structure , but to provide an elastic layer between the segment assembly and the hub or shaft carrying it, which excludes radial pressure loading of the hub or width. The entire tension of the reinforcement rings can be used to generate the arch pressure.

Another known construction leads to the same result (DE-A 2 019 200). In this known commutator, a space is provided between the insulation on the inner surface of the segment assembly and the hub carrying the commutator. The connection of the segment assembly with the hub is made via two washer-shaped membranes, which are connected to the hub in the area of their inner edge and to the end faces of the segment assembly in the area of their outer edge and therefore allow the tension of the reinforcing rings to be fully implemented in the arch pressure of the segment assembly .

It has been shown, however, that the thermally induced deformation of the brush running surface still appears disruptively in these two known commutator constructions.

The invention has for its object to provide a commutator of the type mentioned, which has no or at least a significantly lower thermal deformation than the known commutators.

This object is achieved with the features of claim 1.

The solution according to the invention is based on the consideration that, in the case of commutators of the arch pressure type, the radial forces emanating from the armored segment assembly and resulting from the arch pressure are effective due to the inevitable material inhomogeneity and dimensional asymmetry of the segment association over the circumference thereof in different size distributions. They bring about an individual balance adjustment for each commutator with appropriate rejection of the segment association already during its manufacture. The deformation caused by the warping of the segment assembly is eliminated by overturning it on the finished commutator, but the different size distribution of the radial forces over the circumference of the segment assembly is retained. A renewed deformation of the segment assembly and thus the brush tread is therefore preprogrammed and, due to the weak reaction forces of the reinforcement elements specially designed to absorb centrifugal forces and to maintain sufficient arch tension, but only to a small extent stiff bending, operational stress will occur.

Already as a result of the centrifugal force stress, the radial forces prevailing over the circumference of the segmental compound of unequal size together with the radial components resulting from an inevitable unbalance of the segmental compound result in an increase in the size differences in the radial forces effective across the circumference of the segmental compound in the course of a constant expansion of the segmental bandage that is increasing as the speed increases . The steady heating of the commutator that starts during operation leads to an increase in the asymmetry of the segment assembly due to the heat-induced increase in vault pressure and the increase in pressure and heat resulting from the inhomogeneity of the segment assembly, in particular the insulating lamellae, as a result of the superposing forces a further increase in the size differences of the radial forces acting over the circumference of the segmental association. Added to this is the fact that, due to the relatively soft, orthotropic segment structure, the reduction or build-up of the radial forces acting over the circumference of the segment structure occurs over relatively large distances. This means that when centrifugal and, in particular, heat stress occurs, the equilibrium of forces is adjusted via a correspondingly large expansion of the segment assembly, which thereby increasingly loses its original shape and orientation to the commutator hub and is only connected to the commutator hub as a result of its deformation due to local, uncontrollable contact .

In order to prevent these deformations of commutators of the arch pressure type, such a commutator would have to have a high degree of material homogeneity and dimensional symmetry. The fulfillment of the necessary requirements, e.g. true-to-the-angle, matching thickness segments, largely tolerance-free insulating lamella thickness and homogeneous material, an ideal, axially and radially symmetrical structure of the segment assembly during its manufacture until the commutator is finished, as far as they can be realized, would cause high costs.

For the commutator according to the invention, however, no higher degree of material homogeneity and dimensional symmetry is required than with the known commutators of the arch pressure type, so that the segment association only causes the usual manufacturing costs. The fact that no disturbing deformation of the brush running surface occurs even under dynamic and thermal stress, which is far above the limit reached so far, is due to the fact that the shape behavior of the commutator is largely dependent on the radial as an active component in the mechanical structure of the commutator preloaded hub and / or armature shaft is determined. Their extremely hard spring characteristics and the high potential energy incorporated into them in the course of the manufacture of the commutator have the effect that even slight deformations of the segment assembly from the hub and / or shaft lead to support forces directed radially onto the inner lateral surface of the segment assembly. This means that the supporting forces of the pressurized, extremely flexurally rigid, i.e. counteracting a change in the shape and size of their cross section very high resistance forces counteracting hub and / or shaft against an onset of deformation in the form of substantially higher reaction forces. Advantageously, the supporting forces introduced are chosen to be substantially higher than the amount that is ever reduced as a result of thermal and centrifugal force loads on the commutator during later operation. As a result, the segment assembly is always oriented via an intimate frictional connection to the commutator hub and a correspondingly high reaction of the supporting forces when deformation occurs is guaranteed in each of the operating states that occur later.

Every radial force that tries to expand the segment assembly and thus the reinforcement as a result of operational stress is immediately followed by the corresponding supporting forces of the hub being reduced in an extremely short way. This means that under operational stress there is no significant, stress-related increase in the diameter of the segment assembly, the vault tension prevailing in the vault pressure surface remains largely constant over all operating conditions and the radial pressure between the reinforcement and the segment zones serving as a support changes only to a small extent. Another advantage that results from this is that manufacturing-related deviations of the hub or armature shaft from the roundness or eccentricities do not have a disadvantageous effect.

Due to this property of the commutator according to the invention and the associated radial pressure of the segments against the reinforcement, which is largely the same over all operating states, a relatively low arch pressure is sufficient to prevent individual segments from migrating on the still cold, but subject to centrifugal force. A significant reduction in the arch pressure results with the same armoring compared to a commutator of the arch pressure type in that the armored segment assembly is widened so much in the course of the manufacture of the commutator that a predominant stress component of the armoring, the non-positively coupled hub and / or armature shaft and the insulation radially prestressed between it and the segment assembly.

In a preferred embodiment, however, the area of the segments and insulating lamellae under arching stress is additionally reduced to a dimension that is still required dynamically and is still necessary in terms of production technology. This reduction in the area under vaulting, which can be achieved through recesses and / or deposits of the segments and / or the insulating lamellae, further reduces the radial forces caused by heating and caused by inhomogeneity and dimensional asymmetry, since the heating-related expansion of the Segment association or increase in vault tension is significantly reduced because of the considerable reduction in the areas generating the compressive forces in the circumferential direction. Due to the substantial reduction in vault pressure in the greatly reduced vault pressure area, the forces acting under heat in the segment assembly are greatly reduced and, as a result of the support effect emanating from the hub, the segment ends receiving the reinforcements are relieved.

In order to make the support of the segment assembly on the hub or armature shaft as rigid as possible, or in other words, to make the coupling between the segment assembly and the hub or armature shaft as tight as possible, it is expedient to measure the insulation thickness measured in the radial direction choose between the hub and the shaft and the segments as small as possible, taking into account the required dielectric strength and the aspects to be taken into account during production, whereby at the same time a good heat flow from the segment assembly to the hub and / or armature shaft is achieved.

Advantageous further refinements of the commutator according to the invention are the subject of claims 2 to 9

The invention is also based on the object of providing a method for producing the commutator according to the invention which is as simple as possible to carry out.

This object is achieved with the features of claim 10.

Advantageous further developments of this method are the subject of claims 11 to 18.

• Fig. 1 einen schematisch und unvollständig dargestellten Längsschnitt eines erfindungsgemäßen Kommutators mit den im dynamisch und thermisch unbeanspruchten Zustand wirksamen Kräften,
• Fig. 2 einen Schnitt entsprechend Fig. 1 mit den im dynamisch und thermisch beanspruchten Zustand wirksamen Kräften,
• Fig. 3 eine Seitenansicht eines Segmentes für einen Kommutator gemäß den Fig. 1 und 2 im Zustand vor dem am Segmentverband erfolgenden Andrehen der umlaufenden Stufen für die Armierungsringe,
• Fig. 4 eine Stirnansicht des Segmentes gemäß Anspruch 3,
• Fig. 5 eine Seitenansicht einer Isolierlamelle für den Kommutator gemäß den Fig. 1 und 2 vor dem Einstechen der Ringnuten für die Armierungsringe,
• Fig. 6 eine Stirnansicht der Isolierlamelle gemäß Fig. 5,
• Fig. 7 einen unvollständig dargestellten Längsschnitt eines Ausführungsbeispiels des erfindungsgemäßen Kommutators in einer Bauweise mit Spannschrauben,
• Fig. 8 einen Längsschnitt eines anderen Ausführungsspiels mit Spannschrauben,
• Fig. 9 einen unvollständig dargestellten Längsschnitt eines weiteren Ausführungsbeispiels,
• Fig.10 einen unvollständig dargestellten Längsschnitt eines gegenüber dem Ausführungsbeispiel gemäß Fig. 9 abgewandelten Äusführungsbeispiels.
• Fig.11 einen unvollständig dargestellten Längsschnitt eines fünften Ausführungsbeispiels vor der Fertigstellung
• Fig.12 einen unvollständig dargestellten Längsschnitt des fünften Ausführungsbeispiels im fertigen Zustand.

The invention is explained in detail below on the basis of exemplary embodiments shown in the drawing. Show it:

• 1 shows a schematically and incompletely illustrated longitudinal section of a commutator according to the invention with the forces acting in the dynamic and thermally unstressed state,
• 2 shows a section corresponding to FIG. 1 with the forces acting in the dynamically and thermally stressed state,
• 3 shows a side view of a segment for a commutator according to FIGS. 1 and 2 in the state before the rotating steps for the reinforcing rings are turned on the segment assembly,
• 4 is an end view of the segment according to claim 3,
• 5 shows a side view of an insulating lamella for the commutator according to FIGS. 1 and 2 before the piercing of the ring grooves for the reinforcement rings,
• 6 is an end view of the insulating lamella according to FIG. 5,
• 7 shows an incompletely illustrated longitudinal section of an embodiment of the commutator according to the invention in a construction with clamping screws,
• 8 is a longitudinal section of another execution game with clamping screws,
• 9 shows an incompletely illustrated longitudinal section of a further exemplary embodiment,
• 10 shows an incompletely illustrated longitudinal section of an exemplary embodiment modified compared to the exemplary embodiment according to FIG. 9.
• 11 shows an incompletely illustrated longitudinal section of a fifth exemplary embodiment before completion
• 12 shows an incompletely shown longitudinal section of the fifth embodiment in the finished state.

The segment assembly of the commutator shown in FIGS. 1 and 2, which can withstand high dynamic and thermal loads, is a hollow cylindrical body which is composed of segments 1 and insulating lamellae 2. One of these, consisting of micanite, plate-shaped insulating lamellae 2 lies between two segments 1 made of copper.

The segments 1, whose cross-sectional profile is shown in FIG. 4, have a shoulder 1 'on both side surfaces along their outer edge. These two deposits 1 'reduce the thickness of the segment in the outer edge zone to such an extent that there is no longer any noteworthy arch pressure on the finished commutator. Furthermore, the segments 1 are provided with two symmetrical openings 3 spaced apart in the longitudinal direction of the commutator, which are punched out of the segment and differ in shape from an elongated hole in that they have radii of different sizes at both ends. The smaller radius is provided at the end adjacent to the other opening. The web 4 present between the two openings 3 is located centrally between the ends of the segment.

5 and 6 show, the insulating plates 2 each have three circular, equally large punched-out portions 5, which are arranged at equal distances from one another in the longitudinal direction of the commutator. The central punch 5 lies in the middle between the two ends of the insulating lamella. It is therefore aligned with the web 4. Since the centers of curvature of the openings 3 and the centers of the punched holes 5 have the same distances from the inner circumferential surface of the segment assembly, the partial overlap shown in FIGS. 1 and 2 results. In the areas of the deposits 1 ', the surface pressure between the segments 1 and the insulating slats 2 very low. No arch pressure is transmitted in the areas covered by the openings 3 and punched-out areas 5. A vault pressure can therefore only be generated practically in the surface area between the openings 3 and the punched-out portions 5 on the one hand and the inner lateral surface of the segment assembly on the other hand and the two offset end zones, each of which has an insulated reinforcement ring 6 on the outside. The step for receiving the reinforcement ring 6 is turned out on the composite segment assembly in order to ensure uniform contact with all segments.

The armored segmental assembly sits concentrically with the interposition of insulation 7 a metallic hub 8, which in turn sits on a shaft 9. The insulation 7, the hub 8 and the shaft 9 are prestressed in the radial direction, the latter two parts forming an extremely rigid, largely material-homogeneous and dimensionally symmetrical body, from which support forces S of equal magnitude are produced in an almost ideal manner.

If the hub 8 and the shaft 9 were not preloaded in the radial direction, the armored segment assembly, as in the known commutators of the arch pressure type, would only sit positively on the hub 8, then the clamping force F generated by the reinforcement rings 6 would have a very high arch tension and therefore generate a relatively large resulting radial force G _R. As a result of the expansion of the segment assembly under the influence of the supporting forces S or their radially effective resultants S, however, the radial force G _{R of} the arch tension is reduced to the much smaller value G _r .

In operation, as shown in FIG. 2, the centrifugal force Z claims the lamella group in the same direction as the radial force G _r 'generated by the arching stress. However, since the preloaded hub 8 and the preloaded shaft 9 have a very hard spring characteristic, the centrifugal force Z compensated without a significant radial movement of the segment by a corresponding reduction in the supporting forces S 'or their radial components S _r '. The change in vault tension in the reduced zones that still transmit the vault pressure is therefore slight under the influence of centrifugal force. Accordingly, the difference in size of the resulting radial forces G is small when the commutator is stationary and G _r 'when the commutator is rotating.

Since the increasing arch tension is only effective in the reduced zones of adjacent segments when the commutator is heated, the resulting radial force G ',' is also relatively small and is compensated for by a correspondingly low reduction in the radially active supporting forces S ' _r .

The sum of all forces acting in the radial direction during operation of the commutator is only slightly higher than the sum of these forces on the stationary commutator. This means that under operational stress there is no significant, stress-related increase in the diameter of the segment assembly, the residual arch tension prevailing in the reduced arch pressure area remains largely constant over all operating conditions and the radial pressure between the reinforcement rings 6 and the end zones of the segments serving as a support is only slight changes. In addition, since the radially effective supporting forces are essentially reduced only by the centrifugal force Z, large supporting forces radially starting from the hub, which counteract any deformation of the segment assembly, are still effective even under full operating stress.

In the embodiment of the commutator according to the invention shown in FIG. 7, the segment assembly is composed of alternating segments 11 and insulating lamellae 12. The segments 11 have a shoulder 11 'on both sides along their outer edge zone adjacent to the running surface for the brushes. Furthermore, they are provided with openings 13, which are offset from punched holes 15 of the insulating lamellae 12 such that they are aligned with the webs 14 between the punched holes 15. As a result, as in the exemplary embodiment according to FIGS. 1 to 6, the vault pressure zone is essentially limited to the area between the openings and punched-out areas and the inner lateral surface of the segment assembly and the two end zones, which lie within two reinforcing rings 16 which are made of steel and lie in end-face ring grooves with the interposition of insulation.

In its two end sections, which in the exemplary embodiment each extend over about a third of the total length of the segment assembly, the inner lateral surface of the segment assembly forms an inner cone that widens outward. On these two inner cones there are two steel, insulated support rings 20, the outer surface of which forms a corresponding outer cone. With their cylindrical inner circumferential surface, the two support rings 20 each lie on the cylindrical outer circumferential surface of a steel half-hub 21 and 21 ', the inner circumferential surfaces of which form a bore for receiving a shaft. Through bores lying parallel to the longitudinal axis of the commutator in one half hub 21 and threaded bores 22 aligned therewith in the other half hub 21 'take up clamping screws 23 which are arranged uniformly distributed over the circumference of the half hubs. As shown in FIG. 7, the half-hubs 21 and 21 'each have an annular flange which engages behind them on the outside of the support ring 20, as a result of which the support rings 20 are also tightened to the same extent by tightening the half-hubs 21 and 21' by means of the clamping screws 23. A potting compound 24 fills the gaps between the armoring rings 16 and the segments 11 and the insulating lamellae 12 on both ends of the commutator and covers the outwardly facing end faces of the armoring rings 16, the support rings 20 and the end sections of the segments 11 and insulating lamellae 12 lying between them towards the outside, in the exemplary embodiment the outward-facing side of the casting compound 24 being aligned with the adjacent end face of the half-hub. Of course, the support rings 20 can be omitted, for example if the Hub halves 21 and 21 ', for example due to a large bore, are relatively thin-walled if the hub halves, with the interposition of insulation and their outer cone surface designed as an outer cone, bear against the corresponding inner cone of the segment assembly and are clamped together by means of the clamping screws 23.

This commutator is manufactured in such a way that the armored segment assembly is heated to a temperature which is somewhat higher than the operating temperature of the commutator. The two half hubs 21 and 21 'are preferably pressed in during this heating together with the support rings 20 arranged on them. The segment assembly is expanded until it comes into contact with a stop ring that receives the segment assembly during this manufacturing process. The support rings 20 are preferably shrunk onto the half-hubs 21 and 21 'in order to avoid any air between them, their insulation and the half-hub. The half hubs and the support rings are held under the press-in pressure until the segment assembly has cooled again. Therefore, the expansion is chosen so that the required radial preload of the half-hubs 21 and 21 'and the support rings 20 is achieved after the segment assembly has cooled. Now the two half hubs are screwed together using the clamping screws 23. Finally, the two end faces of the segment assembly and the support rings 20 are cast by means of the casting compound 24.

The structure of the segment structure of the exemplary embodiment shown in FIG. 8 differs from the segment structure of the exemplary embodiment according to FIG. 7 only in that the two reinforcement rings 36 are designed as pressure rings, each with an inner cone, which rests on an outer cone that the inner flank of the reinforcement ring rests on partially receiving, frontal annular groove of the segment assembly forms. The reinforcing rings 36 made of steel are provided with an insulation enveloping them, as in the other exemplary embodiments.

Another difference from the exemplary embodiment according to FIG. 7 is that in addition to a support ring 40, a clamping ring 45 is arranged so as to be longitudinally displaceable on the two half-hubs 41 and 41 '. The two insulated support rings 40 are designed like the support rings 20 and are preferably shrunk onto the half hub carrying them in order to avoid any air between them, their insulation and the half hub. You are also engaged by an annular flange of the half-hub to be tightened to the same extent when clamping the half-hubs. Each of the two clamping rings 45 has, following a cylindrical surface on which the outer, cylindrical part of the inner circumferential surface of the reinforcing ring 36 rests, a radially outwardly projecting ring flange which rests on the outwardly facing end face of the clamping ring. A plurality of threaded holes 42, which are evenly distributed over the circumference and parallel to the longitudinal axis of the commutator, in one clamping ring 45 and through holes aligned with them in the two half-hubs 41 and 41 'and in the other clamping ring 45 each serve to accommodate a clamping screw 43 with which the two clamping rings 45 and thus the reinforcement rings 36 are clamped together. The two half-hubs 41 and 41 'are also alternately provided with threaded holes 46, which are arranged offset to the through holes for the clamping screws 43, also parallel to the longitudinal axis of the commutator and evenly distributed on the circumference, with which the respectively associated through holes in the other half hub 41' or 41 and the tension rings 45 carried by them are aligned. In these holes there are clamping screws 47, by means of which on the one hand the half hub 41 via the support ring 40 carried by it, with its outer cone resting on the inner cone of the segment assembly with the clamping ring 45 carrying the reinforcing ring 36, and on the other hand the half hub 41 'via the support ring 40 with the opposite ring ring 36 carrying clamping ring 45 are clamped together. The clamping screws 47, which clamp the half hub 41 'together with the clamping ring 45, which is displaceably arranged on the opposite half hub 41, are not shown in FIG. 8.

This commutator is manufactured in such a way that the segmental structure is given a vaulted tension by a shrinking process, for example by means of a conical bushing, via which the segmental structure is pressed into a thick-walled, cylindrical pressure socket. Then, by tightening the clamping screws 43, the two clamping rings 45 and together with these the two reinforcement rings 36 are clamped together and the reinforced segment assembly is pressed out of the pressure bush. The two tensioned reinforcement rings now take over the maintenance of the arch tension in the segment association. The segment assembly is then heated to a temperature which is above the later operating temperature, and, preferably in the course of this heating, the half-hubs 41 and 41 'and the support rings 40 carried by them are pressed in with axial pressure. the segment assembly being widened, as in the exemplary embodiment according to FIG. 7, until it lies against a stop ring or a stop bush which receives the segment assembly during this manufacturing process. The two half-hubs are kept under this axial pressure until they cool down. Subsequently the clamping screws 47 are tightened. Due to the widening of the segment assembly and its subsequent shrinking when cooling, the two half-hubs 41 and 41 'and the support rings 40 receive a radial preload which is reduced during operation of the commutator, but is not completely removed.

The armored segment structure of the exemplary embodiment according to FIG. 9 differs from that of the exemplary embodiment according to FIG. 7 only in that its inner lateral surface is also cylindrical in the end sections. Deposits 51 'of the segments 51 and openings 53 of the same and punched-out sections 55 of the insulating lamellae 52 therefore also limit the arching tension here essentially to the area between the cut-out sections and cut-outs on the one hand and the inner surface area on the other hand and the two end zones located within the reinforcing rings 56. Between the cylindrical outer circumferential surface of a hub 58 made of steel and radially prestressed and the inner circumferential surface of the segment assembly there is a molding material 57 which isolates the segment assembly from the hub and transmits the radial forces. The press material 57, which is a mass customary in commutator construction for press commutators, also covers the end faces of the reinforcement rings 56 and the end zones of the lamellar assembly which they encompass and fills the ring grooves receiving the reinforcement rings, insofar as the reinforcement rings do not. To produce such a commutator, the armored segment dressing is heated by heating to a press die temperature required for processing the press material 57, which can be up to over 200 'depending on the press material, and by the press material 57 inserted under pressure between the inner surface of the segment dressing and the hub 58 widened until the outer lateral surface abuts on a press bushing which receives the segmental association. The inside diameter of this press sleeve and thus the degree of expansion of the segment assembly is chosen so that when the segment assembly cools and the shrinkage associated therewith, the hub 58 and the press material 57 lying between it and the segment assembly receive the required radial prestress.

Thanks to this simple manufacturing process and its simple structure, this commutator represents a particularly economical embodiment of the commutator according to the invention.

The exemplary embodiment shown in FIG. 10, like the exemplary embodiment according to FIG. 9, is a ring-armored press commutator. However, it differs from the latter not only in that, in addition to the reinforcement rings 76 provided at both ends of the segment assembly, a third reinforcement ring 76 'is arranged at half the length, which is particularly advantageous with a longer commutator length. A difference also lies in the fact that the reinforcement rings 76 and 76 'are insulated from the segments 71 by press material 77 which, when pressed, fills the space between the reinforcement rings and the grooves receiving them. The third reinforcement ring 76 'also requires a slightly different design of the openings 73 in the segments and the punched-out areas 75 of the insulating lamellae located between them, as shown in FIG. 10. Thanks to these recesses and openings as well as the stepped portions 71 'of the segments 71, the arch pressure zone, that is the surface area of the segments and insulating lamellas in which the arch tension is effective, is also greatly reduced in this exemplary embodiment.

A further difference between the exemplary embodiment according to FIG. 40 and that according to FIG. 9 is that the bare hub 78 made of steel has a conical outer surface. Instead of this one-piece hub or a shaft with an outer cone, two half-hubs with an outer cone could also be used.

The commutator according to FIG. 10 is produced in such a way that, like a press commutator, the prestressed segment assembly, in which the hub 78 has not yet been inserted, is pressed with press material 77, which completely embeds the reinforcement rings 76 and 76 '. As shown in FIG. 10, the molding material 77 completely covers the two outer reinforcement rings 76 and the end sections of the segments 71 lying inside them, and in the exemplary embodiment is flush with the hub end face. The annular slot is also completely filled with molding material, via which the annular groove containing the third reinforcement ring 76 'is connected to the inner lateral surface of the segmental association. The insulating layer formed by the molding material 77 on the inner surface of the segment assembly has a conical inner surface corresponding to the outer cone of the hub 78. After the segment assembly has been pressed out with the molding material 77 and before it is tempered, the armored segment assembly is heated to a temperature above the later operating temperature and as a result of this, as well as the pressing of the hub 78, which preferably takes place in the course of the heating, to the extent predetermined by a stop ring or the like. When cooling, the hub 78 then receives the required radial preload. The hub 78, which is initially held slightly longer than the commutator and slightly protrudes on both sides after being pressed in, is now turned off flush with the ends of the commutator. By the subsequent tempering the press material becomes harder.

In addition to the advantages, which also the embodiment according to FIG. 9 has, the commutator according to FIG. 10 has the advantage that pre-punched segments and insulating lamellae can be used, i.e. no processing of the segment assembly to produce the seats required for the reinforcement rings and none Insulation of the reinforcement rings is necessary.

The exemplary embodiment shown in FIGS. 11 and 12 differs from the previously described exemplary embodiments in particular in that already in the course of the reduction in diameter required for the arch pressure build-up of the segment assembly composed of segments 91 with openings 93 as well as recesses 91 'and insulating lamellae 92 with punched-outs 95, e.g. by means of a conical bushing, via which the segment assembly is pressed into a pressure bushing 100, a relatively thin-walled, insulated hub sleeve 101 is shrunk into the receiving bore of the segment assembly and connected to it in a force-locking manner. Since a correspondingly high shrinkage path or a large reduction in diameter is required for the relatively soft, orthotropic segmental structure to build up its arch tension, the amount of compression of the hub sleeve 101 can be reduced by reducing the diameter by specifying a difference between the diameter of the receiving bore of the segmental structure and the outer diameter the insulated hub sleeve 101 can be determined. After it has been pressed into the pressure bushing 100, an annular groove is screwed in at both ends for receiving an insulated reinforcing ring 96 at each end. The compression of the hub is chosen so high that after the reinforcement rings 96 have been shrunk onto the segment ends exposed by the annular groove and the armored segment assembly has been removed from the pressure bushing 100, the segment assembly to a large extent with a substantial reduction in the arch tension and increasing tension build-up in the reinforcement rings 96 expands by the high supporting forces of the compressed hub sleeve 101. The segmental association radially prestressed by the hub sleeve 101 is then heated. A hub 98 is pressed in.

The hub sleeve 101, which is shrunk into the segmental structure as a pressure sleeve, could also have a slightly conical bore. The hub or armature shaft provided with a corresponding outer cone could then be pressed in as the segment assembly heats up. A conical hub has the advantage that, since it has already been introduced and pressurized in the course of the heating of the segment assembly in the receiving bore, it supports the ends of the segments 91 carrying the reinforcing rings 96. The coefficient of expansion of the segment assembly is namely greater than that of the reinforcing rings 96 made of steel. The segments 91 therefore experience increasing bending stress at their ends when heated.

The hub sleeve is wrapped in a thin insulating tape that surrounds it like a coil and forms double insulation 97 of the segment assembly with respect to the armature shaft. Good heat dissipation to the armature shaft is ensured by the two very thin insulating layers between the segment assembly and the hub 98 or armature shaft. The resulting low heat gradient between the segment assembly and the hub and / or the armature shaft contributes to the fact that the reduction of supporting forces of the hub remains extremely low. This effect of good heat dissipation from the commutator to the armature shaft naturally also applies to the other exemplary embodiments. Furthermore, the insulation can of course also be formed by such a winding in other exemplary embodiments.

Claims (18)

1. Commutator with a reinforced segment assembly and which through an interposed insulation (7; 57; 77; 97) is rotationally rigidly disposed on a hub (8; 21; 21'; 41; 41'; 58; 78; 98; 101) or armature shaft (9), characterised in that the hub (8; 21; 21'; 41; 41'; 58; 78; 98; 101) and/or armature shaft (9) as well as the insulation (7; 57; 77; 97) are initially tensioned radially by an essential tensioning portion in the reinforcement (8; 18; 38; 58; 78; 98) of the segment assembly, all segments (1; 11; 51; 71; 91) of the segment assembly being in all operating conditions force-lockingly coupled to the hub (8; 21; 21'; 41; 41'; 58; 78; 98; 101) and/or the armature shaft (9) by the bracing forces (S: Sr) which as a reaction to the radial initial tensioning are directed against the inner shell face of the segment assembly and are positioned in a radial direction in relation to the hub and/or armature shaft.

2. Commutator according to Claim 1, characterised in that the widening out of the reinforced segment assembly is sufficiently great that the bracing forces for the segment assembly on the stationary commutator arising out of the radial initial tensioning of the hub (8; 21; 21'; 41; 41'; 58; 78; 98; 101) and/or the armature shaft (9) are greater than the diminution of these bracing forces brought about by dynamic and thermal loading and and the resultant variation in the form of the commutator in operation.

3. Commutator according to Claim 1 or 2, characterised in that measured in a radial direction the thickness of the insulation (7: 97) between the hub (8; 21; 21'; 41; 41'; 58; 78; 98; 101) or shaft (9) on the one hand and the segment assembly on the other lies in the lower limit range of the value required on electrical and mechanical grounds.

4. Commutator according to one of Claims 1 to 3, characterised in that to reduce the radial forces between adjacent segments (1; 11; 51; 71; 91) caused by inhomogeneity and dimensional asymmetry, and the breakdown of bracing forces due to increasing arch pressure when the commutator is heated, the arch pressure zone is reduced in size by cut-outs (3; 5; 13; 15; 53; 55; 73; 75; 93; 95) and/or steppings (1'; 11'; 51; 71; 91') on the segments and/or the insulating plates (2; 12; 52; 92) of the segment assembly.

5. Commutator according to Claim 4, characterised by, extending along the outer edge of each segment and/or each insulating plate and over the entire axial length of the segment assembly, at least one stepping (1'; 11'; 51'; 71'; 91

6. Commutator according to Claim 4, characterised in that the cut-outs (3; 13; 53; 93) in the segments (1; 11; 51; 91) are directed at the webs (14) between the cut-outs (15; 55; 95) in the insulating plates (12; 52; 92).

7. Commutator according to one of Claims 1 to 8, characterised in that the hub is sub-divided into two half-hubs (21; 21'; 41; 41') tensioned in respect of each other by screws (23) and disposed at a distance from each other in an axial direction, each of which carries an insulated conical thrust ring (20; 40) which is form-lockingly connected to the half-hub carrying it in terms that its entrainment by the half-hub upon a movement towards the other half-hub, its conical outer surface bearing on a corresponding internal cone in the segments assembly.

8. Commutator according to one of Claims 1 to 8, characterised in that the hub is sub-divided into two half-hubs tensioned towards each other by screws and disposed at a distance from each other in an axial direction, each of which has a conical outer face bearing through an insulation on a respective corresponding inner cone in the segment assembly.

9. Commutator according to Claim 7 or 8, characterised by, adapted to be clamped together by means of clamping screws (43), two clamping rings (45) disposed for axial displacement on one or other half-hub (41; 41'), and, constituting the reinforcement on the segment assembly, two insulating rings (38) with an inner cone, each of which bears on an outer cone of an annular groove in the segment assembly being clamped towards each other in an axial direction by means of the two clamping rings (45).

10. A method of producing a commutator according to Claim 1 in which a reinforced segment assembly is disposed on a metallic hub or armature shaft through an interposed insulation and concentrically in rotation to the longitudinal axis of the hub or shaft, characterised in that the segment assembly is widened out evenly and in that a radial pre-tensioning which maintains this widening out through radial thrust forces, is applied to the insulation as well as to the hub and/or shaft.

11. A method according to Claim 9, characterised in that the insulation as well as the hubs and/or armature shaft are sufficiently pre-tensioned that even upon a dynamic and thermal loading of the segment assembly such as occur in operation, the segment assembly is still maintained force-lockingly coupled to the hub or armature shaft by the radial bracing forces.

12. A method according to Claim 9 or 10, characterised in that the reinforced segment assembly becomes heated to a point above the working temperature of the commutator and in that preferably during the course of this heating, a one-piece or two-part hub with an outer cone or a conical armature shaft is through an interposed insulation pressed into the conical receiving bore, an abutment ring engaging around the segment assembly limiting the widening out of the segment assembly which is brought about by the pressing-in of the hub or armature shaft.

13. A method according to Claim 10 or 11, characterised in that by being heated to a temperature which corresponds to the pressing tool temperature needed to process a moulding material and by a forcing in of moulding material between its inner surface and the hub or armature shaft, the reinforced segment assembly is widened out until its outer surface comes to bear on a bush which accommodates the segment assembly during forcing-in of the moulding material, the widening out being sufficiently great that after the forced out segment assembly has cooled, the necessary radial pre-tensioning of the hub or shaft is present.

14. A method according to Claim 10 or 11, characterised in that a one-piece or two-piece hub sleeve is, through an interposed insulation, fitted into the loosely assembled segment assembly and during the course of the reduction in diameter of the segment assembly which is required to build up the arch pressure, is shrunk into tne assembly and in that reinforcing rings are then shrunk onto the segment ends which are exposed by annular grooves, the compression of the hub sleeve which has occurred at least over a part of the diameter reduction of the segment assembly being sufficiently great that after ejection of the reinforced segment assembly from a thick-walled bush which holds it under arch tension, the segment assembly is to a considerable degree widened out with a substantial reduction in arch tension and increasing build up of tension in the reinforcing rings due to the high bracing or thrust forces of the compressed hub sleeve.

15. A method according to Claim 14, characterised in that the radially pre-tensioned reinforced segment assembly which contains the hub sleeve is heated to beyond the working temperature of the commutator after which a hub or the armature shaft is pressed in or a subcooled hub or armature shaft is fitted.

16. A method according to Claim 14 or 15, characterised in that during the course of heating of the segment assembly a hub or armature shaft provided with an outer cone is pressed into the hub sleeve which has a corresponding outer cone.

17. A method according to one of Claims 12 to 18, characterised in that heating of the segment assembly takes place inductively, mainly via the reinforcement of the segment assembly.

18. A method according to one of Claims 10, 11 or 12 to 17, characterised in that the insulation between the segment assembly and the hub is constituted by an insulating strip which bakes under heat and which is wrapped around the member carrying the insulation, at least one overlap being formed between successive windings which pass through the member in an axial direction.

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