EP2426793A1 - Abrasive ring brush system for current controlled synchronous motor rotor - Google Patents

Abstract

The system (2) has slip rings fastened to a rotor (4), and brushes arranged in a rotatably fixed part. The slip rings are formed at a rigid printed circuit board and united with the board by an insulating casing to form an integrated slip ring unit (14). The slip rings are arranged coaxially and at a radial distance from each other, and in cooperation with each of the brushes. The brushes are oriented in an axial direction of the rotor. The ring unit is fastened to a front side of the rotor in a torsionally stiff manner, and to a support ring (5) that supports a winding head (7) of the rotor.

Description

FIELD OF THE INVENTION

The present invention relates to a slip ring brush system, which is preferably suitable for the transmission of exciting current to the rotor of a current-excited synchronous motor for main drives of electric vehicles.

As is known, the dimensioning of the exciting current transmission from the stationary motor housing to the rotating shaft plays an important role in electrically excited electric motors, in particular in the case of current-excited synchronous motors (SSM). Without this external power supply, this motor behaves like a reluctance motor, apart from the slight magnetization of any permanent magnets. The uninterrupted power supply of the rotor windings is thus a basic prerequisite for making the advantages of the current-excited synchronous motor practically usable. Due to the current excitation can be waived on the use of high-quality magnets from rare earths. The increasing worldwide demand for rare earths, combined with the limited production capacity, increase the importance of the development of a current-excited electric motor and, consequently, the need for a cost-effective, conductive rotor current transfer with brush and slip ring.

STATE OF THE ART

In electric rotary machines with a high power output and a high efficiency is preferred, the electrical loss of To reduce brushing as much as possible, since the electrical loss in the brush significantly affects the overall efficiency of the rotary electric machine. One known way of reducing electrical loss uses brushes made of graphite and a conductive metal, particularly copper.

• ■ Kohlebürsten für Gleichstrommotoren (Anlasser-, Lüfter-, Scheibenwischer- und Stellmotor, Motor der Benzinpumpe)
• ■ Kohlebürsten für Wechselstrommotoren (vorrangig in Haushaltsgeräten: Staubsauger, Quirl und Mixer)

The application of carbon brush and slip ring is very large and can be divided into two areas:

• ■ Brushes for DC motors (starter, fan, windscreen wiper and servomotor, motor of the fuel pump)
• ■ Carbon brushes for AC motors (primarily in household appliances: vacuum cleaner, whisk and mixer)

In the design of brushes and slip rings in the current-excited synchronous motor, however, can be used only conditionally to the current state of the art, since the boundary conditions differ from the previous applications.

In current-excited synchronous motors currently only radial brush arrangement are used for slip ring. In the case of the radial brush arrangement of conventional generators or motors, as a rule the entire motor power is conducted via the brushes, which requires a particularly large dimensioning of the brushes.

Rarely, axially arranged carbon brushes are used in practice, e.g. used in a wet running fuel pump, or as grounding contact of a railway and for the lightning protection of wind power rotors.

Typically, carbon brushes are arranged radially on the shaft.

From the DE-102008059994 A1 is a typical electric rotary machine, namely a starter motor is known in which radially acting Brushes are pressed on slip rings, which are fixed to the rotor shaft, to pass an exciting current electrically to the field winding on the rotor.

A disadvantage of the above slip ring brush system with radial brushes is that on the one hand it requires a large installation space in the machine housing for the use of brushes and slip ring, on the other hand, the change or repair of the brushes are too cumbersome and labor intensive. However, this hardly plays a role in a starter motor, since its duty cycle is low and therefore usually corresponds to the life without brush replacement the life of the motor vehicle. The size in turn is accepted because the starter motor is relatively small in comparison to the rest of the engine.

However, the situation is different for rotor machines for the propulsion of electric vehicles. There, these two disadvantages are not desirable. In particular, for the use of power-driven synchronous motors in electric vehicles, a small footprint of the electrical transmission system and a low service requirements or good accessibility for a possible upcoming brush change is required.

Essence of the invention

The invention has for its object to provide an improved slip ring brush system for transmitting electrical excitation current to a rotor of rotary electric machines, such as electric motors, in particular electrically excited synchronous motors for electric vehicles, through which reduces the above-mentioned disadvantages of the prior art, or can be eliminated. In addition, special needs of the electromobility should be perceived optimized, without significantly increasing the cost of the brush system.

• ■ Eine kontinuierliche und störungsfreie Stromübertragung zwischen relativ zueinander rotierenden Elementen elektrischer Rotationsmaschinen;
• ■ Eine kompakte Anordnung der Bürsten-Elemente mit leichter Zugänglichkeit der Bürsten, die als Verschleißteile einfach austauschbar sein sollten.
• ■ Eine geringe axiale Baulänge der Rotationsmaschine

By the system according to the invention should therefore be realized:

• ■ A continuous and trouble-free power transmission between relatively rotating elements of rotary electric machines;
• ■ A compact arrangement of the brush elements with easy accessibility of the brushes, which should be easily replaceable as wear parts.
• ■ A small axial length of the rotary machine

The objects are achieved by the features of independent claim 1. Advantageous further developments of the solution according to the invention are specified in the dependent claims.

However, in the exemplary proposed field of application of an axial brush arrangement, only about 2% of the rated power - as an excitation power - is conducted via the brushes. For a safe operation of this electric motor, a continuous brush contact with the slip ring is particularly important in this solution.

• ■ Bauraumneutralität: Dies bedeutet eine Kompatibilität zu allen herkömmlichen Elektromotoren mit Permanentmagnetantrieb (z.B.: IPM), wobei die Außen-geometrie des Motors unverändert beibehalten aber die Innengeometrie der Lageschilde anpassbar ist;
• ■ Minimaler Bauraum für das Schleifring-Bürsten-Systems trotzt axialer Bürstenposition (Bisher wurde in der Fachwelt eher von einer Baulängenerhöhung durch axiale Bürsten ausgegangen);
• ■ Bürsten sollen möglichst einfach auszuwechseln sein: Die Erfindung sieht daher ein en bloc auswechselbares Bürstenpaket mit Steckverbindung vor, so dass bei guter Zugänglichkeit der Bürstenwechsel schnell erfolgen kann;
• ■ Wicklungsverschaltung ist mithilfe einer kunststoffumspritzten Leiterplatte bewerkstelligt. Daraus ergibt sich einerseits Variationsfreiheit in der Polverschaltung bei identischer Rotorbewicklung, andererseits jedoch auch eine bessere und wirtschaftlichere Basis für Schleifringe;
• ■ Schleifringe sind erfindungsgemäss einerseits integriert, andererseits aber voneinander hinreichend abgetrennt, um Luft- und Kriechstrecken einzuhalten;
• ■ Durch die Erfindung ergibt sich eine zuverlässige mitdrehbare Befestigungsmöglichkeit der Schleifringe stirnseitig am Rotor.
• ■ Durch die Erfindung wird vor allem bei den hohen Drehzahlen von Hauptantrieben (bis ca. 12000 U/min) ein Bürstenfeuer unterbunden. Ähnlich dem Überdrehen der Schleifringe bei radialer Anordnung bietet die Leiterplatte die Möglichkeit einer nachträglichen, spanabtragenden Bearbeitung um damit den notwendigen Planlauf zu erreichen. Andererseits sind die Leiterplatten problemlos plan herstellund montierbar, so dass sich diesbezüglich ein Vorteil gegenüber den hülsenförmig aufzuziehenden Schleifringen ergibt.
• ■ Die erfindungsgemässe Ausbildung der Schleifringe erhöht zwar die die Umfangsgeschwindigkeit wenigstens eines Schleifrings gegenüber einer radialen Anordnung auf der Welle, dies hat jedoch auch den positiven Nebeneffekt, dass durch die erhöhte Fliehkraft eine verbesserte Reinigung der Isolationsteile der Schleifringe von Kohlenstaub erfolgt.

The following inventive findings particularly influenced the inventive concept and the subsequent development of the invention of the slip ring brush system according to the invention, as follows:

• ■ Space neutrality: this means compatibility with all conventional permanent magnet electric motors (eg: IPM), maintaining the motor's outer geometry unchanged, but adapting the internal geometry of the bearing shields;
• ■ Minimum installation space for the slip ring brush system defies axial brush position (Up to now, it has been assumed in the professional world rather by an increase in length by axial brushes);
• ■ Brushes should be as simple as possible to replace: The invention therefore provides an en bloc interchangeable brush package with connector, so that with good accessibility, the brush replacement can be done quickly;
• ■ Winding connection is accomplished by means of a plastic-coated printed circuit board. This results on the one hand freedom of variation in the pole circuit with identical rotor winding, on the other hand, however, a better and more economical basis for slip rings;
• ■ Slip rings according to the invention on the one hand integrated, on the other hand, but sufficiently separated from each other to comply with air and creepage distances;
• ■ The invention results in a reliable mitdrehbare attachment possibility of the slip rings frontally on the rotor.
• ■ By the invention, a brush fire is suppressed, especially at the high speeds of main drives (up to 12000 U / min). Similar to the over-rotation of the slip rings in a radial arrangement, the circuit board offers the possibility of a subsequent, chip-removing machining in order to achieve the necessary axial runout. On the other hand, the circuit boards can be easily manufactured and assembled plan, so that there is an advantage in this respect over the sleeve-shaped slip rings to be created.
• Although the inventive design of the slip rings increases the peripheral speed of at least one slip ring relative to a radial arrangement on the shaft, this also has the positive side effect that the increased centrifugal force improves the cleaning of the insulating parts of the slip rings of pulverized coal.

Thus, the invention has been based on the above-discussed known slip ring brush system for transmission of electrical signals or excitation current to a rotor of rotary electric machines, in particular current-excited synchronous motors, which is provided with attached to the rotor slip rings, and with fixedly arranged brushes. Each of the brushes is in each case one of the slip rings in a current-transmitting friction connection.

The essence of the invention is seen in the fact that the slip rings are combined together with at least one printed circuit board and at least one insulating sheath to form an integrated slip ring unit. In this integrated slip ring unit, the slip rings are coaxial and spaced apart from each other at a radial distance and cooperate with the electrical power transmission brushes. The integrated slip ring unit is centered on the front side of the rotor and fixed in a torsionally rigid manner. The brushes are oriented / arranged in the axial direction of the rotor.

Since this system can equally be used to transmit signal currents (e.g., to evaluate a temperature sensor on the rotor, it is not limited to excitation current transmission but is generally applicable to signal transmission between the rotor and non-rotating parts of the motor.

In a preferred embodiment, the integrated and axially loaded slip ring unit is frontally on the rotor by one, the winding heads of the rotor against axial and radial loads supporting Attached support ring. The integrated slip ring unit is preferably designed annular disc-shaped.

Such an embodiment of the invention is conceivable in which in the radial distance between the coaxial and in the installed state preferably in the same vertical plane lying slip rings of the integrated slip ring unit an additional electrical breakdown insulation is installed. As a result, the breakdown resistance for higher voltages can be further increased.

In terms of process technology, it is advantageous if the insulating sheathing of the integrated slip ring unit is designed as a plastic extrusion coating.

In the preferred embodiment of the invention, the axial brushes are combined in an insulating housing to form an integrated brush unit. As a result, the integrated brush unit as a whole can be easily and quickly replaced. For this purpose, it is also expedient if the integrated brush unit is provided with an electrical plug connection, which preferably dissolves alone by removing the brush unit and connects by attaching the brush unit.

Preferably, the brushes of the integrated brush unit are made of electrographite "E43", and the slip rings of the integrated slip ring unit made of CuSn10 (copper-tin) to limit the wear in the slip ring brush system according to the invention exclusively to the brush wear, the electrical contact resistance Minimize and keep the brush wear as low as possible. The choice of brush material is closely linked to the choice of material for the slip ring. In this respect, if necessary, other combinations can be selected.

The compact, inventive slip ring brush system can preferably be installed in a relatively small installation space of a current-excited synchronous motor which is axially bounded by a support ring of the rotor and a bearing plate of the synchronous motor, and in the radial direction of the bearing plate and stator winding.

BRIEF DESCRIPTION OF THE DRAWING

• Figur 1 eine Teilschnittansicht eines stromerregten Synchronmotors mit einem Ausführungsbeispiel des erfindungsgemäßen Schleifring-Bürsten-Systems;
• Figuren 2A-2C Ansichten der Teile der erfindungsgemäßen integrierten Schleifringeinheit des Schleifring-Bürsten-Systems nach Fig. 1, im vergrößerten Maßstab;
• Figur 3 eine perspektivische Ansicht der integrierten Schleifringeinheit nach Fig. 2C mit zwei axial angeordneten Bürsten;
• Figur 4 eine perspektivische Ansicht des Ausführungsbeispiels der erfindungsgemäßen integrierten Bürsteneinheit des Schleifring-Bürsten-Systems nach Fig. 1;
• Figuren 5 und 6 zerlegte perspektivische Darstellungen der integrierten Bürsteneinheit nach Fig. 4;
• Figur 7 eine perspektivische Ansicht des Ausführungsbeispiels der erfindungsgemäßen integrierten Bürsteneinheit nach Figuren 5 und 6 in zusammengebautem Zustand;
• Figur 8 eine Schnittansicht der integrierten Schleifringeinheit entlang der Linien VIII-VIII in Figur 3.

The invention will be explained in more detail below with reference to the accompanying figures, which illustrate a preferred embodiment of the solution according to the invention. It shows:

• FIG. 1 a partial sectional view of a current-excited synchronous motor with an embodiment of the slip ring brush system according to the invention;
• Figures 2A-2C Views of the parts of the integrated slip ring unit according to the slip ring brush system according to the invention Fig. 1 on an enlarged scale;
• FIG. 3 a perspective view of the integrated slip ring unit after Fig. 2C with two axially arranged brushes;
• FIG. 4 a perspective view of the embodiment of the integrated brush unit of the slip ring brush system according to the invention after Fig. 1 ;
• FIGS. 5 and 6 decomposed perspective views of the integrated brush unit after Fig. 4 ;
• FIG. 7 a perspective view of the embodiment of the integrated brush unit according to the invention after FIGS. 5 and 6 in assembled condition;
• FIG. 8 a sectional view of the integrated slip ring unit along the lines VIII-VIII in FIG. 3 ,

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

Fig. 1 shows a partial sectional view of a current-excited synchronous motor 1 in particular for main drives of electric vehicles, with a first embodiment of the slip ring brush system 2 according to the invention, which aims to reliably transmit an electrical excitation current to a rotor 4 of the current-excited synchronous motor 1.

The slip ring brush system 2 according to the invention can be used mutatis mutandis in all other fields of application of electrical rotary devices in which between them relatively rotating units electrical signals or electrical current - in particular excitation current - to be transmitted.

On the rotor 4 is in this embodiment ( Fig. 1 ) a protective device (so-called "restraint system") provided to support both sides of the rotor 4 from a laminated core 6 in the axial direction projecting end windings 7 at higher speeds of the rotor 4 against the loads on both sides by means of a support ring 5. The two support rings 5 are preferably connected by axial screws 9 with a predetermined bias; This creates a compact and rigid rotor package. In Fig. 1 is a stator lamination with 8, a stator winding with 10, a bearing plate with 11, a rotor shaft with 12 and a rotation axis of the rotor 4 denoted by 13.

In the excitation current transmission with brushes and slip ring is - similar to permanently excited motors - the high dynamics of the Motos a basic requirement for the excitation current transmission. For electric motors for Electric vehicles can reach speeds in excess of 12000 rpm and power over 100 kW.

Thus, in addition to avoiding the disadvantages of expensive magnetic material, the per se known disadvantages of known slip ring brush systems are accepted in favor of high engine dynamics. However, the state of the art in this regard has not yet progressed to meet the complex requirements of such a current-excited synchronous motor. Therefore, additional electrotechnical development effort has been required to effect an improvement in exciting current transfer between brushes and slip rings. This is solved by the present invention.

Concerning the possible placement of the slip ring brush system 2 in the synchronous motor 1, the requirements which are set to the installation position and the transmission system were first defined in a targeted manner. The requirement for the space neutrality, which allows compatibility with all previous applications and thus at any time a change already installed electric motors, is to be regarded by the applicant as an important prerequisite.

• ■ Möglichts minimaler Bauraum für das Schleifring-Bürsten-System; Das Schleifring Bürstensystem nutzt im Wesentlichen den Raum innerhalb der stehenden Statorwickelköpfe der Erregerwicklung und kann von axialer Seite gewartet/ausgetauscht werden. D.h. es kann von der Stirnseite her auf die Bürsten zugegriffen werden und benötigt das Maschinengehäuse von radial her keine Zugriffsmöglichkeit. Dies erleichtert die Wartung und kommt den als Mechaniker geschulten KfZ-Werkstätten-Personal entgegen.
• ■ Integrierte Schleifringeinheit - einfach zu montieren, geringes Gewicht, hohe Laufruhe; minimaler axialer Bauraum
• ■ Wechselbares integriertes Bürstenpaket mit Steckverbindung;
• ■ Variationsfreiheit für die Wicklungsverschaltung mithilfe einer kunststoffumspritzten Leiterplatte der integrierten Schleifringeinheit.

According to the invention, the following concept of exciting current transmission is accomplished:

• ■ Possible minimal installation space for the slip ring brush system; The slip ring brush system essentially uses the space inside the stationary stator winding heads of the field winding and can be serviced / replaced from the axial side. That is, it can be accessed from the front side on the brushes and requires the machine housing from radially forth no access. This facilitates the maintenance and comes to meet trained as a mechanic automotive repair shop staff.
• ■ Integrated slip ring unit - easy to assemble, low weight, high smoothness; minimal axial space
• ■ Changeable integrated brush package with plug connection;
• ■ Freedom of variation for the winding connection with the aid of a plastic-coated printed circuit board of the integrated slip ring unit.

Starting from the in Fig. 1 illustrated installation situation could now be developed in the sense of the invention, a new concept for main drives of electric vehicles for power transmission from the stator 3 to the rotor 4. Contrary to the traditional arrangement of carbon brushes in the radial direction, as described in the prior art, according to the invention an axial arrangement of the brushes and a new slip ring brush system has been realized.

Both the slip ring design and the brushes can be installed in the available space of the engine. In addition, the DC connection from a rotor power converter / regulator to the electric motor and optionally some electronic components (not shown) for improved operation in the space are integrated. This is possible because the brushes are arranged on one side of the motor shaft.

For the purposes of the present invention, the proposed slip ring brush system 2 in the second detailed embodiment (see Fig. 3 ) from an integrated slip ring unit 14 and two, the slip ring unit 14 associated and axially positioned brush 15th

The brushes 15 according to the invention are preferably assembled as a completely replaceable integrated brush unit 16 (this will be described below in connection with FIG Figures 4-7 described in detail). Of course, within the scope of the invention, a variant in which the brushes can be exchanged individually by about - like conventional carbon brushes - can be removed from the brush housing individually. In terms of a short service time and easy installation, however, the integrated and pluggable solution is preferred.

The details of the integrated slip ring unit 14 according to the invention are shown in FIG Figures 2A-2C and 8th illustrated. The preferred embodiment of the slip ring unit 14 consists of a printed circuit board 17 as a starting material (illustrated individually in FIG Fig. 2A ), Slip rings 18 and 19 and an insulating sheath 20, preferably as a plastic sheath. In Fig. 2B are the circuit board 17 with the associated two slip rings 18 and 19, and in Fig. 2C the complete integrated slip ring unit 14, together with the circuit board 17, the two slip rings 18-19 and the enclosure 20 (see. 2b to see). As in Fig. 2C can be seen, the integrated slip ring unit 14 is formed here ring-disc-shaped.

In Figures 2C and 8th Also, coaxial annular grooves 21 and 22 are provided in the enclosure 20 to make the two slip rings 18 and 19 of the integrated slip ring assembly 14 accessible to the brushes. The axially disposed brushes (not shown) cooperate with the abrasive surfaces of the slip rings 18 and 19 by a spring-loaded sliding frictional engagement. On the other hand, the slip ring unit 14 is provided along its circumference with recesses 23 ( Fig. 3 ), are passed through which screws, not shown, on the one hand to attach the slip ring unit 14 frontally on the support ring 5 of the rotor core coaxially ( Fig. 1 On the other hand, to connect the circuit board 17 with the windings in a suitable manner.

The integrated slip ring unit 14 is thus according to the invention reliable, rigid and co-rotatably mounted on the front side of the rotor 4 to a trouble-free Friction contact with the axial brushes 15 at any time to produce or maintain.

This integrated slip ring unit 14 is the embodiment after Fig. 1 mounted directly on the support ring 5, which is supported by feet (not shown in detail) directly to the rotor core 6 sheet. As a result, the slip rings 18 and 19 are the integrated slip ring unit 14 and an end face of the support ring 5 of the rotor core substantially in a common vertical plane, which is arranged perpendicular to the rotation axis 13.

Details of the structure and the mounting of the support ring 5 are the patent application EP10169565.8 The same applicant, which is hereby incorporated into later (possibly priority-based) combinations of the teachings of this cited application with the present, as a reference by reference.

With this improved attachment of the integrated slip ring assembly 14, there are no such problems with the brushes 15 when rotating the rotor 4 - even at higher speeds of 12,000 rpm - as in the prior art. Due to the high number of revolutions also centrifugal forces act on the slip rings 18 and 19. Since these are radially out of the rotor shaft 12, they are better cleaned due to the higher centrifugal forces of any abrasion or dust.

As in Fig. 1 can be seen, a relatively small installation space for the integrated slip ring unit 14 is available, which is bounded axially to the left of the rotor core 6, axially to the right of the integrated brush unit 16 and the end plate 11, and in the radial direction by the end plate 11 and the stator winding 10.

1. a) Integration der Schleifringe, d.h. die integrierte Schleifringeinheit 14; Diese Maßnahme ist mit dem Vorteil verbunden, dass jeder Schleifring als separates Bauelement hergestellt werden kann, welches abhängig von den jeweiligen Prüfstandversuchen in der Zukunft durch Veränderung des Material jederzeit einfach angepasst werden kann;
2. b) Freiheit bei der Verschaltung der einzelnen Polwicklungen, d.h. Verbindung der Drahtenden:
   • Bei einem sechspoligen (3 Polpaare) Blechschnitt ergeben sich damit folgende Möglichkeiten der Wicklungsverschaltung: 3 x 2 parallel oder 6 x seriell. Dies ist vorteilhaft, da gleicher Fertigungsprozess mit Variationsfreiheit der Wicklungsverschaltung eine Entkopplung von Wicklungsprozess und Verbindung der zwölf Drahtenden zueinander ermöglicht Die Erfindung kann jedoch auch bei anderen Konstruktionen mit mehr als zwei Erregerstrompolen verwendet werden, indem entsprechend mehr konzentrische Schleifringe an der Leiterplatte ausgebildet werden. Die erfindungsgemässe Ausführung der Schleifringeinheit ist hierbei auch exklusive der Wicklungsverschaltung denkbar. Die Wicklungsverschaltung kann dabei über die Drahtführung realisiert werden, wobei trotzdem die Funktionalität bzw. die Vorzüge der beschriebenen Schleifringeinheit erhalten bleiben. In diesem Fall würden minimal zwei Drahtenden mit der Schleifringeinheit kontaktiert werden.
3. c) Isolations-Trennwand 30 der Schleifringe 18 und 19 voneinander in der integrierten Schleifringeinheit 14 zur Kooperation mit der Bürsteneinheit 16. Diese Maßnahme ist deshalb bevorzugt, da aufgrund der-für erhöhte Dynamikanforderungen - hohen Spannungen die Luft- und Kriechstrecken auf diese Weise einzuhalten sind, um damit sowohl einen Überschlag als auch einen Masseschluss unterbinden zu können.

For the purposes of the invention, the following functions are purposefully integrated into this installation space:

1. a) integration of the slip rings, ie the integrated slip ring unit 14; This measure has the advantage that each slip ring can be manufactured as a separate component which, depending on the respective test bench tests, can be easily adapted at any time by changing the material at any time;
2. b) freedom in the interconnection of the individual pole windings, ie connection of the wire ends:
   • In the case of a six-pole (3-pole pair) sheet metal section, this results in the following possibilities of winding connection: 3 x 2 parallel or 6 x serial. This is advantageous because the same manufacturing process with freedom of variation of the winding interconnection allows a decoupling of winding process and connection of the twelve wire ends to each other. However, the invention can also be used in other constructions with more than two exciter current poles by correspondingly more concentric slip rings are formed on the circuit board. The inventive embodiment of the slip ring unit is also conceivable exclusive of winding interconnection. The winding interconnection can be realized via the wire guide, while still maintaining the functionality or the advantages of the described slip ring unit. In this case, at least two wire ends would be contacted with the slip ring unit.
3. c) isolation partition wall 30 of the slip rings 18 and 19 from each other in the integrated slip ring unit 14 for cooperation with the brush unit 16. This measure is preferred because of the - for increased dynamic requirements - high voltages creepage and clearance must be maintained in this way to do with it both to prevent a rollover and a ground fault.

A basis for implementing the above three functions according to the invention, on the one hand, forms the printed circuit board 17 of the integrated slip ring unit 14 (FIG. Fig. 2A ) into which the copper wire ends (not shown) can be soldered and connected together by a corresponding layout. This circuit board 17 is then equipped with two copper rings, ie the slip rings 18 and 19 ( Fig. 2B ) and thus electrically connected in a corresponding manner. This means that contacts or printed conductors (not shown) of the printed circuit board 17 are connected in the correct polarity on the one hand to rotor windings 7 and on the other hand to the slip rings 18 and 19.

• ■ Einerseits als stoffschlüssige Verbindung zwischen den verwendeten Komponenten - namentlich der Leiterplatte 17 und den Schleifringen 18 und 19 - da die Verbindung z.B. durch Einlöten physikalisch aufgrund der großen Fliehkraftbelastungen nicht immer ausreichend ist;
• ■ Andererseits als elektrische Isolation der integrierten Schleifringeinheit 16, welche durch die freie geometrische Gestaltung den jeweiligen funktionalen Anforderungen einfach angepasst werden kann.

Since the radial installation space and the creepage and clearance distances to be maintained behave in opposite directions, the printed circuit board 17 equipped with the slip rings 18 and 19 is, as already mentioned, provided with an enclosure 20 for increasing clearance and creepage distances as the third element of the slip ring unit 14 (FIG. Fig. 2C ), preferably by plastic extrusion. This envelope 20 of the integrated slip ring unit 14 (FIG. Fig. 2C ) serves:

• ■ On the one hand as a material connection between the components used - namely the circuit board 17 and the slip rings 18 and 19 - because the connection is not always sufficient, for example by soldering physically due to the large centrifugal loads;
• On the other hand as electrical insulation of the integrated slip ring unit 16, which can be easily adapted by the free geometric design of the respective functional requirements.

In Figure 2C For example, the integrated slip ring unit 14 is formed as an annular unit. Between the coaxial and arranged with a radial distance A slip rings 18 and 19, the integrated Slip ring unit 14 with an additional insulating partition 30 (see also Fig. 8 ).

An insulation system designed in this way actually has at least two effects: First, it allows for improved insulation through extended spark gaps or creepage distances, and secondly, brushing in the groove causes any carbon dust deposits to "loosen up" and then from the slip ring due to centrifugal forces away. As a result, a long-term stability of the insulating body is made possible.

With this slip ring brush concept, all necessary functions are realized in the available installation space, thus maintaining the space neutrality. In addition, flexibility in engine design and adaptation, e.g. maintained in the choice of material of the slip rings or the interconnection of the motor windings. This freedom of variation allows a rapid response to new findings and is therefore considered to be a significant advantage.

Of course, the slip rings can already be integrated with the circuit board formed by the slip rings themselves form the tracks of the circuit board. In any case, printed circuit board and slip rings are integrally molded with electrically insulating plastic, which additionally increases the spark gap or creepage distance and improves the rigidity of the slip ring unit 14.

In a particular embodiment of the invention, the plastic partition wall 30 between the slip rings 18 and 19 (FIG. Fig. 8 ) are designed so high that they with a corresponding groove (suggestively in Fig. 6 visible) of the brush unit 16 cooperates and thus a complete shielding of the two brushes 15 against each other in contact with the slip rings 18 and 19 causes. In technical reversal could the brush body have a corresponding projection which runs without friction with an annular groove in the insulating partition wall 30 between the slip rings 18 and 19. Optionally, an additional penetration-preventing material may be poured into the isolation partition 30.

The principle of operation of the axial brushes 15 and the slip rings 18 and 19 is based on minimizing the wear due to high sliding properties, and possibly by selecting a skillful combination of materials to limit the abrasion on the brush 15, since the brushes, in contrast to the slip ring unit, are simply designed interchangeable and thus deliberately "sacrificed" as a wear component.

According to the present invention, however, an axial arrangement of the brushes 15 is proposed ( FIGS. 1 and 3 ). To Fig. 3 Each of the two mutually parallel, axial and stationary brushes 15 - held by each one of the grooves 21 and 22 through - with one of the slip rings 18 and 19 of the rotating integrated slip ring unit 14 frictionally in frictional contact. In Fig. 3 It can also be seen that in this arrangement coal dust from the integrated slip ring unit 14 is always thrown away radially by the high number of revolutions.

The carbon brushes are currently available in very different designs. By using a standardized / industrialized unit, the brush is already pre-dimensioned with tension spring and (paper) insulation (not marked) and is available in a cylindrical design. It is necessary to properly position the individual brushes on the slip ring in the axial direction (tangential to the slip ring) and to perform their electrical connection to a field voltage source as simply as possible. On the other hand, it may be necessary after a long operation to make a brush change due to wear.

In Figures 4-7 is a preferred embodiment of the integrated brush unit 16 according to the invention. This integrated brush unit 16 is designed as a replaceable unit. It consists of an insulating housing 24, preferably made of plastic, which is equipped with two brushes 15, for example carbon brushes. The housing 24 ( Fig. 4 ) is provided with a removable cover 25 which is fixed to the housing 24 - after inserting or changing at least one of the two brushes 15 - by screws 26. The integrated brush unit 16 is provided with further screws 27 which serve for fastening the brush unit 16 in its axially adjusted or oriented position for the slip ring unit 14, eg in a recess (not shown) of the end shield 11. The integrated brush unit 16 can therefore be easily and quickly replaced as a whole when the brushes 15 are ground.

For connection and interchangeability of the integrated brush unit 16, a plug-in connection is provided, by means of which the integrated brush unit 16 can be electrically connected to the exciting current supply. As in Figures 5-7 is shown, two plug contacts 31 are provided on the one hand on the housing 24, on the other hand to a contacting element 32 to this connector. The housing 31 can be easily removed from the contacting element 32 to release the plug contacts 31.

Different brush materials are available for the different fields of application. The brushes 15 are optionally also used from precious metals (and their alloys) only with increased demands on the contact quality. However, high temperatures and increased mechanical loads in terms of brush speed are to be expected, such as for electric motors for main drives of electric vehicles, then Carbon materials (eg hard coal, carbon graphite, specialty graphite, electrographite, metal graphite, etc.) are used.

However, the selection of brush material is closely related to the choice of material for slip ring 18-19. For example, the carbon of the brush 15 diffuses - in a pair of copper graphite - in the oxidized surface of the copper slip ring and acts there both hardening and lubricating, which is also to be considered.

In order to limit wear on the slip ring brush system 2 according to the invention to brush wear only, materials are available for the slip rings 18-19, e.g. a slip ring of Cu or Cu alloys, CuZn, CuSn, Ag or Ag alloys, Au or Au alloys, steel, or a coating of Ni or Co, or of galvanized Au layer.

• Die bevorzugte elektrische Materialpaarung ist C72/CuAg0.1 (Bürste/Schleifring).
• Die bevorzugte mechanische Materialpaarung ist E43/CuSn10 anzusehen, d.h. die Bürsten 15 sind aus Elektrographit "E43" und die Schleifringe 18-19 sind aus CuSn10 (Kupfer-Zinn) gefertigt.

It has been proved by test-bench cycle tests that the material pairings proposed on our part for the rotor current transmission are distinguished by the axial brush 15 and slip ring 18-19. We preferred two material pairings:

• The preferred electrical material pairing is C72 / CuAg0.1 (brush / slip ring).
• The preferred mechanical material pairing is E43 / CuSn10, ie the brushes 15 are made of electrographite "E43" and the slip rings 18-19 are made of CuSn10 (copper-tin).

Both the choice of material and the dimensions of the brushes 15 and the slip rings 18-19 requires great experience in this field. Due to the sensitive, usually opposing influence of many parameters, often only an estimate is possible. Because of our longtime However, experience has put together some parameters that could be used to carry out an inventive design.

One of these parameters is the current density in the brush 15. As is known, in addition to the limitation due to the electrical overload, a lower limit of the current density must also be maintained in order to minimize the wear of the brush 15. In the case of an electrographite brush, the current density in our experiments was between 4.0-16.0 [A / cm ² ], with short-term overload it was around 30.0 [A / cm ² ]. This brush 15 gave very good results especially at high slip ring speeds (around 88.0 - 96.0 m / s).

A second but also important dimensioning criterion is the temperature. Due to the mechanical friction between the brush and the slip ring and the electrical power loss due to the resistance in the brush, increased temperatures occur directly at the brush. The effects of temperature on wear behavior are very complex. It can be stated that a temperature range of 60-90 ° C is a preferred range according to our experiments. This ensures a suitable formation of the oxide layer, which in turn is indispensable for a low brush wear.

Heat is introduced into the slip ring via the brush surface, which must be released again via the remaining ring surface in order to remain in thermal equilibrium. Therefore, our goal was also to keep the brush area as small as possible in relation to the other slip ring surface. Due to the low excitation power, the cross-sectional area of the axial brushes 15 (see Fig.1 ) are kept very low.

In Fig. 1 are a connection box 28 for electrical safety components and external power supply, as well as an electrical connection element 29 between the brush unit 16 and the junction box 28 shown only schematically with dashed lines.

• Kontinuierliche und störungsfreie Signal- oder Stromübertragung mit hoher Dynamik sogar bei stromerregten Synchronmotoren mit hoher Drehzahl;
• Bauraumneutralität, d.h. eine Kompatibilität hinsichtlich äusserer Motorgeometrie für verschiedene Elektromotortypen;
• Kompakte Konstruktion und minimale Baulänge bei axialer Bürstenposition (vgl. die Ausnutzung des Hohlraums unter bzw. innerhalb der Statorwickelköpfe 10 in Fig.1);
• Zuverlässige stirnseitige Befestigungsmöglichkeit der integrierten Schleifringeinheit 14 am Rotor;
• Kompakte und leicht auswechselbare integrierte Bürsteneinheit 16 mit elektrischer Steckverbindung;
• Flexibilität hinsichtlich der Motorauslegung und Anpassung in der Materialauswahl der Schleifringe 18 und 19 und der Bürsten 15, sowie der Verschaltung der Motorwicklungen;
• Kontinuierliche Gleichstromübertragung insbesondere bei Fahrzeugantrieben;
• Den Durchmesser des Motors, sowie die Bürstengeschwindigkeit zu reduzieren, was zu einem geringeren Verschleiß führt.

In summary, it should be noted that at least the following advantages can be achieved by the slip ring brush system 2 according to the invention:

• Continuous and trouble-free signal or current transmission with high dynamics, even with high-speed synchronous motors with high power;
• Bauraumneutralität, ie a compatibility with respect to external motor geometry for different types of electric motors;
• Compact construction and minimum length at axial brush position (see the utilization of the cavity under or inside the stator winding heads 10 in FIG Fig.1 );
• Reliable end-face mounting possibility of the integrated slip ring unit 14 on the rotor;
• Compact and easily replaceable integrated brush unit 16 with electrical plug connection;
• Flexibility with regard to motor design and adaptation in the material selection of the slip rings 18 and 19 and the brushes 15, as well as the interconnection of the motor windings;
• Continuous direct current transmission, in particular for vehicle drives;
• To reduce the diameter of the motor, as well as the brush speed, resulting in less wear.

The invention is of course not limited to the described embodiment. Also other embodiments and combinations are conceivable within the claimed scope of protection due to the above disclosure.

LIST OF REFERENCE SIGNS:

• 1 - Current-excited synchronous motor
• 2 - slip ring brush system
• 3 - stator
• 4 - rotor
• 5 - Support ring
• 6 - rotor laminated core
• 7 - winding head
• 8 - stator laminated core
• 9 - screw
• 10 - stator winding
• 11 - end shield
• 12 - rotor shaft
• 13 - rotation axis
• 14 - Integrated slip ring unit
• 15 - brush
• 16 - Integrated brush unit
• 17 - circuit board
• 18 - slip ring
• 19 - slip ring
• 20 - wrapping / plastic coating
• 21 - groove
• 22 - groove
• 23 - hole
• 24 - housing
• 25 - cover
• 26 - screw
• 27 - screw
• 28 - Connection box
• 29 - connecting element
• 30 - insulating partition
• 31 - Plug contact
• 32 - contacting element

Claims (12)

Slip ring brush system for transmitting excitation current to a rotor of rotary electric machines, in particular electrically excited synchronous motors, with slip rings attached to the rotor and fixedly mounted brushes in a non-rotatable part, each of the brushes having one of the slip rings in a current transmitting sliding friction connection, characterized in that the slip rings (18, 19) are formed on a rigid printed circuit board (17) and joined thereto by an insulating sheath (20) to form an integrated slip ring unit (14) in which the slip rings (18, 19) are coaxial and from each other with a radial distance (A) are arranged and with each of the brushes (15) cooperate, wherein the brushes (15) in the axial direction of the rotor (4) are oriented, and that the integrated slip ring unit (14) frontally on the rotor (4) is fixed in a torsionally rigid manner. The slip ring brush system according to claim 1, characterized in that the printed circuit board (17) of the integrated slip ring unit (14) contacts or interconnects which polrichtig connected on the one hand with rotor windings (7) and on the other hand with the slip rings (18,19) are. The slip ring brush system according to claim 1 or 2, characterized in that the integrated slip ring unit (14) on a, the winding heads (7) of the rotor (4) supporting the support ring (5) is fixed frontally. The slip ring brush system according to any one of claims 1-3, characterized in that the integrated slip ring unit (14) is designed ring-disc-shaped. The slip ring brush system according to any one of claims 1-4, characterized in that at the radial distance (A) between the coaxial slip rings (18, 19) of the integrated slip ring unit (14) an additional electrical insulating partition wall (30) preferably made of Plastic is incorporated, in which optionally further penetration-preventing material - optionally made of paper or the like. - is poured. The slip ring brush system according to any one of claims 1-5, characterized in that the insulating sheath (20) of the integrated slip ring unit (14) is formed as a plastic extrusion. The slip ring brush system according to any one of claims 1-6, characterized in that the axial brushes (15) are combined in a common housing (24) to form an integrated brush unit (16). The slip ring brush system according to claim 7, characterized in that the integrated brush unit (16) is formed replaceable as a whole module. The slip ring brush system according to claim 7 or 8, characterized in that the integrated brush unit (16) is provided with an electrical plug connection (31, 32) for connection to a field current source. The slip ring brush system according to any of claims 1-9, characterized in that the axial brushes (15) are made of electrographite "E43". The slip ring brush system according to any one of claims 1-10, characterized in that the slip rings (18, 19) of the integrated slip ring unit (14) consist of CuSn10 (copper-tin alloy). The slip ring brush system according to any one of claims 1-11, characterized in that the slip ring brush system (2) in the current-excited synchronous motor (1) can be installed or installed in an installation space, which axially by a support ring (5 ) of the rotor (4) and of a bearing plate (11) of the synchronous motor (1), as well as in the radial direction by the end plate (11) and the winding head of a stator winding (10) is limited.

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