STATOR FOR AN ELECTRICAL MACHINE AND PROCEDURE FOR THE PRODUCTION OF A STATOR

1. Field of the Invention

The present invention relates to a stator for an electrical machine including a plurality of stator coils arranged on a stator yoke and an interconnection arrangement arranged on one end face of the stator yoke having connecting conductors which are electrically insulated from one another and arranged concentrically with respect to one another. Each connecting conductor has a different diameter. The connecting conductors have connections for connection to the ends of the stator coils and for connection to the electrical machine. The present invention also relates to a method for producing such a stator.

2. Description of the Related Art

Stators for electrical machines generally have a plurality of stator teeth on which stator coils are wound. The coils are associated with individual phases of electrical power. The coils associated with a common phase are interconnected. In a three-phase machine the stator has three phases. Each of the phases have current applied to them separated by phase angles of 120°. The current input and the current output from the individual coils are passed out of the electrical machine at one stator end.

In known stators, the individual coils are interconnected by hand. In doing so, the individual coil ends of each coil were routed to the respective connections for connection to the electrical machine and electrically connected there. However, this type of interconnection has a number of disadvantages. For example, the separate interconnection of the individual coils to the corresponding connections for connection to the electrical machine results in thick cable harnesses which add to the space requirements of the electric machine. Space requirements are becoming more important in many applications. For example, a stator of the above-described type intended to be used in a vehicle is limited to the amount of area available in the engine compartment. Accordingly, efforts are being made to design individual components used in the engine compartment to be as small and space-saving as possible.

Furthermore, the known method of connecting individual coils requires that the individual wires of the coil ends be carefully insulated from one another. This requirement necessitates the use of additional insulation material and thus leads to a further increase in the required physical space. Finally, there is also a risk that faults can occur when the coil ends are being associated and correspondingly interconnected. Owing to the large number of wires, it is difficult to determine when a coil has been incorrectly connected, and when this situation occurs, which of the coils has been incorrectly connected. If a short circuit occurs in the interconnection arrangement, it is difficult and time consuming to locate the defect point.

Furthermore, the known interconnection arrangement is also highly costly, since the interconnection process must be carried out by hand. Automation of the process for production of such interconnection arrangements is impossible, so that the known interconnection arrangements are not suitable for large-scale production.

A known stator for electrical machines is disclosed in the preamble of claim1in the German reference DE 195 44 830 A1. In this stator, there is no individual interconnection of the respective coils to the connections for connection to the electrical machine. Instead, connecting conductors designed as ring conductors are proposed which are electrically insulated from one another and are arranged concentrically in an insulating slot structure and with a different diameter. The individual coil ends are connected via projections to the connecting conductors, with the projections projecting out of the interconnection arrangement body. This known stator avoids the complex individual interconnection of the individual coils, but this stator also has a number of disadvantages.

For example, this stator as well requires a relatively large amount of area because the interconnection arrangement is arranged in front of the coils in the axial direction. Furthermore, the projections provided for connection of the coil ends to the connecting conductors are aligned in a rigid manner at right angles to the connecting conductors which increases the area requirement for the interconnection arrangement and thus for the entire stator.

Another electrical machine having a stator provided with coils and connecting elements in the form of a ring provided for interconnection of the coils is disclosed in German reference DE 196 47 559 A1. These connecting elements designed in the form of a ring are arranged radially or axially adjacent and are electrically insulated from one another. The connection of the individual coil ends to the connecting conductors is made via openings formed in the conductors. The coil ends are passed through the openings and are then attached. This solution also still requires a relatively large amount of area, since the interconnection arrangement is once again arranged in front of the coils in the axial direction.

It is an object of the present invention to provide a stator for an electrical machine that avoids the problems of the prior art. More specifically, it is an object of the present invention to provide a stator for an electrical machine, in which the production of the individual components and the process of interconnecting the coils may be automated and carried out cost-effectively. Furthermore, the stator is intended to be designed to be particularly space-saving. In particular, the losses which occur in the stator are also intended to be minimized. Furthermore, an appropriately improved method for producing a stator is intended to be provided.

The object of the present invention is achieved by a stator comprising an interconnection arrangement arranged radially inside an area bounded by the stator coils. The connections for the ends of the stator coils comprise connection projections designed such that they project outward to attach the stator coil ends at an angle to the respective connecting conductor. Furthermore, a plurality of cutouts are provided in the interconnection arrangement for the connection projections, into which cutouts the connection projections may be bent or are bent.

The stator according to the present invention allows automatic production of the interconnection arrangement in a simple and cost-effective manner and allows automatic interconnection of the individual coils. At the same time, the area required for the interconnection arrangement, and thus for the entire stator, is considerably reduced compared to the prior art.

A fundamental idea of the present invention is that the stator coils are first fitted to the stator yoke. The connecting conductors are then introduced into the area which is bounded by the stator coils. The connecting conductors have a diameter which is smaller than the diameter of the surface bounded by the coils. Accordingly, the individual connecting conductors are no longer located axially in front of the coils, or their end windings, as has been described with respect to the known solutions. In fact, the connecting conductors are now arranged coaxially with respect to the stator coils, underneath or inside them. The individual connecting conductors preferably have a width which is matched to the end windings of the individual coils, so that the connecting conductors do not project beyond the coils, either in the axial or in the radial direction. The stator thus has a width which is governed only by the coil geometry.

The ends of each of the coils are attached to the connection projections on the connecting conductors. To accommodate this connection, the connection projections are designed such that they initially project at an angle, preferably at an angle of 90°, to the respective connecting conductor. This enables a simple connection of the coil ends to the connection projections.

Once the coil ends have been attached, the connection projections are bent into appropriate cutouts provided in the connecting conductors. In consequence, the axial space occupied by the projecting connection projections is not required after the coil ends have been connected to the connecting conductors.

In principle, the present invention is not limited to specific connecting conductor cross sections. However, it has been found to be particularly advantageous to design the individual connecting conductors with a quadrilateral conductor cross section. This design allows the individual connecting conductors to be pushed into one another in a simple and accurate manner.

Depending on the current conducting requirement, the connections for connection to the electrical machine may be in the form of plugs, sleeves, plug pins, cable lugs or other electrical connections. However, the invention is not limited to the cited examples of electrical connections, so that other embodiments for the electrical connections are also conceivable and possible.

The individual components of the stator according to the present invention may be produced in a simple and cost-effective manner. The individual coils may then be interconnected by an automated process. Furthermore, the particularly advantageous arrangement of the interconnection arrangement inside the area bounded by the stator coils allows the stator to be configured in a particularly space-saving manner. Finally, the configuration of the stator according to the invention, in particular the choice of the cross sections for the connecting conductors, also minimizes any possible resistive heat losses.

The stator may be used for every possible form of electrical machine. Electrical machines in which the stator of the present invention may be installed include, but are not limited to, for example, synchronous machines and especially synchronous machines with permanent-magnet excitation. One machine which is particularly worthy of mention is, for example, the starter generator for vehicles. This is an electrical machine whose rotors are borne via the crankshaft bearing of the internal combustion engine. The starter generator is used not only for starting and stopping the internal combustion engine, but may also carry out various functions during operation of the engine, such as braking functions, booster functions, battery management, active oscillation damping, synchronization of the internal combustion engine, and other functions. The starter generator may comprise an external-rotor synchronous machine and may be connected to the engine block of the internal combustion engine via a stator support as a supporting element.

The connection projections are advantageously arranged in the region of the stator coil ends. This allows the distances between the connection projections and the stator coil ends to be particularly short. This arrangement also prevents faults in the interconnection of the coils of one phase. The coils are interconnected in a clear manner, so that any possible defect in the interconnection of the coils may be easily identified.

An insulating layer is preferably provided between each of the connecting conductors. The insulating layer may advantageously be very thin and may, for example, comprise insulating paper, insulating film or other insulating material. The insulating layer may be loosely arranged between the individual connecting conductors, bonded to the connecting conductors, or fitted between the connecting conductors in some other way. The invention is not limited to specific embodiment forms of the insulating layer or to specific insulating materials.

In a further refinement, the interconnection arrangement may be arranged above an insulating layer on the stator yoke. This insulating layer may, for example, comprise an insulating disk or the like.

The stator coil ends are advantageously connected to the connection projections via a jointed connection and/or a mechanical connection. For example, the coil ends may be soldered to the connection projections using, for example, a soldering or brazing process. It is also conceivable for the coil ends to be welded to the connection projections. Preferred welding processes include resistance welding, laser welding, or ultrasound welding. However, any other welding may also be used. The mechanical connections used may be, for example, crimped connections. However any other mechanical connection for effecting the connection may also be used.

The connections for connection to the electrical machine are preferably each passed from the radial inside of the stator yoke between two adjacent stator coils to the radial outer side of the stator yoke. To do this, the connections may be passed radially outward through the gaps that exist between two adjacent stator coils, leading to a further reduction in the axial physical space.

Each of the connecting conductors are preferably produced from a strip material. This allows the connecting conductors to be produced by an automated process which is particularly easy and cost-effective. The individual connecting conductors may be produced from any suitably conductive material such as copper and may be rolled by a suitable rolling process and wound to form coils. The connection projections, and the cutouts required in the connecting conductors, may be incorporated in the connecting conductors by any suitable method such as, for example, stamping methods, cutting methods or other machining processes.

In a further refinement, one or more of the connecting conductors may have one or more cutouts for the connections to pass through for connection to the electrical machine. Such cutouts are physically necessary since the connecting conductors are arranged radially one above the other, and electrically necessary to prevent electrical contact between the connections and the respective adjacent connecting conductors.

The interconnection arrangement may preferably have three connecting conductors for a three-phase machine.

The number of connecting conductors depends on the application and the embodiment of the stator. In the same way, the number of stator coils used may vary for different stator application areas. Since each of the stator coils is connected via two connection projections to appropriate connecting conductors, the number of connection projections and the number of cutouts for the connection projections may be varied as required when the number of stator coils varies.

The connecting conductors may advantageously be designed in the form of a ring or in the form of a ring segment. This allows the connecting conductors to be matched particularly advantageously to the geometry of the stator and to the arrangement geometry of the stator coils.

According to one preferred embodiment of the stator according to the invention, the connecting conductors are designed as closed ring structures. The end regions of the ring structures are designed as respective connections for connection to the electrical machine. In this embodiment, the individual connecting conductors are produced first of all as strip material and then cut to the required length. After this, the connecting conductors (which are initially in the form of flat strips) are bent to form ring structures with the required diameter. The end regions of the ring segments may then be bent at a desired angle, for example at right angles to the connecting conductor, and thus form a respective connection for connection to the electrical machine. Those end regions which are designed as a connection may advantageously be connected to one another using a suitable joining process, for example, which increases the robustness of the annular connecting conductor.

According to another embodiment of the invention, the connecting conductors may be designed as open ring structures, in which case the individual ring structures may each have a different length. In this embodiment, one of the end regions of a respective ring structure may be designed as a connection for connection to the electrical machine. Such a refinement of the individual connecting elements further simplifies the production. The configuration as an open ring structure and the fact that the individual connecting conductors have a different length eliminates the need for forming cutouts for the connections to pass through.

In yet another refinement to the invention, the connecting conductors may be designed as closed rings, with the connections for connection to the electrical machine each being arranged on the rings. The connections may each be arranged in an appropriate cutout in the connecting conductors. In this embodiment, the respective connections are not required to be formed as specially designed end regions of the connecting conductors. In fact, individual connecting conductors may be produced first of all in the form of closed rings, with the connections then being attached to the connecting conductors. The connections are advantageously once again arranged in appropriately designed cutouts on the connecting conductors. This once again makes it possible for the connections to be passed between the respective adjacent connecting conductors without any possibility of electrical contact between the connections and the respective adjacent connecting conductors.

Each of the stator coils advantageously comprises an end winding and an insulating body and is produced using an individual tooth winding technique. This production technique allows the coils to be wound automatically on the respective teeth. After winding, the individual coil produced in this way is then connected to the stator yoke.

The interconnection arrangement may advantageously be arranged via a jointed connection and/or a mechanical connection on the stator yoke or on the insulating body of the stator coils. This arrangement of the interconnection arrangement must be adopted owing to the natural weight of the interconnection arrangement and the oscillations which occur in the electrical machine. The fixing of the interconnection arrangement is necessary since, otherwise, the coil ends could tear off or be damaged. The interconnection arrangement, and the connecting conductors of the circuit arrangement, may advantageously be arranged on the stator yoke or on the insulating bodies of the stator coils via a clip or by some other type of mechanical attachment such as, for example, screwing, riveting, welding. The connection of the interconnection arrangement to the stator yoke and/or the insulating bodies of the stator coils is not limited to the above listed connections and may be effected by any mechanical connection.

In a further refinement, the stator may be impregnated. This results in a particularly solid structure. The stator, and the individual components of the stator, may, for example, be encased by a high-temperature cast resin, which is electrically insulating and assists thermal conduction to dissipate the heat losses released in the stator coils.

According to the present invention, a method for producing a stator according to the present invention, as described above, is distinguished according to the present invention by the following steps:

a) fitting the stator coils to the stator yoke;

b) introducing the interconnection arrangement which comprises a plurality of connecting conductors which are insulated from one another into an area which is bounded by the stator coils, so that the interconnection arrangement does not project either in the axial direction or in the radial direction beyond the end windings of the stator coils;

c) attaching the stator coil ends to the connection projections of the plural connecting conductors; and

d) bending of the connection projections into the cutouts provided for receiving the connecting conductors.

The method according to the present invention allows simple, cost-effective interconnection of the individual stator coils to the connection conductors which may be automated. The advantages, influences, effects and method of operation of the method according to the invention is described above in the discussion of the stator according to the present invention.

The stator coils are advantageously produced using the individual -tooth winding technique.

In a further refinement, the connecting conductors of the interconnection arrangement are initially produced as strip material and are then cut to the desired length.

In a further refinement, the stator coil ends are attached to the connection projections via a jointed connection and/or a mechanical connection.

The connections for connection of the connection conductors to the electrical machine are preferably each passed through between two adjacent stator coils.

The stator may advantageously subsequently be impregnated.

Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

FIGS. 1to3show a first embodiment of a stator10which is designed for use as a stator for an electrical machine. The present invention is particularly designed for use with a synchronous machine with permanent-magnet excitation such as a starter generator for a motor vehicle.

The stator10has a stator yoke11on which a plurality of stator coils12are arranged. The stator coils12each have an end winding13and an insulating body14. The ends of the stator coil windings13are each formed by stator coil ends15. The stator coils12are arranged around a circumference on the stator yoke11and thus form an area16bounded by the stator coils. This area16has a diameter formed by the distances between the stator coils12and the diameter of the stator yoke11. The height of the area16results from the end windings13of the stator coils12, that is to say from those regions of the end windings13which project beyond the stator yoke11.

An interconnection arrangement20is provided on one end face17of the stator yoke11. The interconnection arrangement20has three connecting conductors21,22,23, which are each designed as a closed ring structure31. Although three connecting conductors are shown, more or less than three connecting conductors could also be used depending on the particular application in which the stator10is used. The connecting conductors21,22,23are produced from a strip material comprising a conductive material such as, for example, copper and each have a different diameter. When the stator10is in the assembled state, as shown inFIG. 2, the connecting conductors21,22,23are designed to be concentric with respect to one another and are thus arranged radially one above the other. Insulating layers24,25,26,27are provided between each of the individual connecting conductors21,22,23and on the radial outer and radial inner side of the entire interconnection arrangement. In the present exemplary embodiment, the insulating layers comprise insulating paper. The insulating layers prevent any electrical contact between the individual connecting conductors21,22,23. Furthermore, the individual connecting conductors21,22,23are attached to the end face17of the stator yoke11via an insulating layer37in the form of an insulating disk.

The connecting conductors21,22,23comprise a plurality of connection projections28for connection of the stator coil ends15to respective connecting conductors21,22,23. The number of connection projections28depends on the number of stator coils12arranged on the stator yoke11. Each stator coil end15is attached to one of the connection projections28in a suitable manner such as, for example, by a soldered or welded connection.

InFIGS. 1to3, the connection projections28to this end initially project at an angle, preferably at right angles, from the respective connecting conductors21,22,23to facilitate the connection to the coil ends15. To minimize the space required by the stator10, cutouts29are provided in the region of the connection projections28in the connecting conductors21,22,23. The connection projections28may be bent so that they are received in the cutouts29after being connected to the stator coil ends15.

The end regions32of the connecting conductors21,22,23which are designed as closed ring structures31, are designed as connections L1, L2, L3for connection to an electrical machine, which is not shown. The end regions32are bent up, i.e., radially outward, in an appropriate manner for this purpose.

To prevent any electrical contact between the connections L1, L2, L3and the respective adjacent connecting conductors21,22,23, appropriate cutouts30are also provided in the connecting conductors21,22,23. The connections of the respective adjacent connecting conductors are passed through this cutout30in each connecting conductor, without any electrical contact being possible.

The individual end regions32of the connecting conductors21,22,23which are designed as a closed ring structure31, are bent in such a way that the end regions32can be passed radially outward, in their function as connections L1, L2, L3, through gaps between two respective adjacent stator coils12, for connection to the electrical machine.

The stator10designed according to the invention may thus be produced in a particularly space-saving manner.

A method for production of such the stator10will now be described. First of all, the individual stator coils12are automatically wound onto individual teeth using a suitable production method such as, for example, using the individual tooth winding technique. The stators coils12wound in this way are then fitted to the stator yoke11.

The individual connecting conductors21,22,23may be produced as strip material, using a suitable method. The individual cutouts29,30and the connection projections28are then formed in the strip material. The strips are cut to the respective desired lengths and then bent to form closed ring structures31. After this, their end regions32are bent such that they form the connections L1, L2, L3for connection to the electrical machine.

The connecting conductors21,22,23, which are designed as closed ring structures31, are pushed together. The diameters differ so that the connecting conductors21,22,23are concentrically arranged one above the other in the radial direction after they are pushed together. Appropriate insulating layers24,25,26,27are fitted between the individual connecting conductors21,22,23. The interconnection arrangement20formed in this way is pushed under the end windings13of the stator coils12and against one end face17of the stator yoke11. In the process, the configuration of the interconnection arrangement20according to the invention results in the individual connecting conductors21,22,23projecting neither in the axial direction nor in the radial direction beyond the end windings13of the stator coils12. The connections L1, L2, L3are passed radially outward through the gaps between two adjacent stator coils12.

The coil ends15are then attached to the connection projections28, which may be done, for example, using a soldering or welding method. After this connection of the coil ends15, the connection projections28are bent into the cutouts29. Accordingly, once the coil ends15have been connected, there is no need for any more axial physical space used by the projecting connection projections28.

The stator10manufactured in this way can be impregnated in a subsequent method step, resulting in a solid structure.

FIGS. 4to6show a further embodiment of the stator10aaccording to the invention. In this case, those components which are physically identical to the corresponding components in the embodiment shown inFIGS. 1to3are denoted by identical reference numbers.

The stator10aillustrated inFIGS. 4to6is constructed in an essentially identical manner to the stator10described with reference toFIGS. 1to3so that, to avoid repetition, the stator yoke11and the coils12will not be described in detail.

In contrast to the exemplary embodiment shown inFIGS. 1to3, the interconnection arrangement20aillustrated inFIGS. 4to6has connecting conductors21a,22a,23awhich are designed in the form of an open ring structure33. The individual connecting conductors21a,22a,23aonce again have a number of connection projections28and cutouts29, via which the stator coil ends15may be connected to the connecting conductors21a,22a,23ain the manner which has already been described in detail further above.

Designing the individual connecting conductors21a,22a,23aas open ring structures33has the advantage that there is no need to form special cutouts for the connections L1, L2, L3to pass through. The individual connecting conductors21a,22a,23aonce again each have different diameters. In addition to this, this embodiment provides for the connecting conductors21a,22a,23ato have different lengths as well. If the connecting conductors21a,22a,23aare now bent to form rings, the different lengths of the individual connecting conductors result in free spaces which carry out the function of cutouts and through which the connections L1, L2, L3of the respective adjacent connecting conductors may be passed.

As can be seen fromFIGS. 4to6, the coil ends15are not always required to be connected to appropriate connection projections28by the shortest route. In fact, even in an embodiment such as this, the length of the coil ends15to be interconnected is still sufficiently short to ensure that the coils12are interconnected in a clear manner.

FIGS. 7to9show yet another embodiment of the stator10baccording to the invention. Physically identical components are once again denoted by identical reference numbers.

In contrast to the exemplary embodiments illustrated inFIGS. 1to6, the stator10billustrated inFIGS. 7to9has an interconnection arrangement20bwhose connecting conductors21b,22b,23bare designed as closed rings35. The closed rings35each have cutouts36in which the respective connections L1, L2, L3for connection to an electrical machine are arranged. The individual cutouts36are in this case designed in such a way that the connections L1, L2, L3can be passed through respective adjacent connecting conductors21b,22b,23bwithout any electrical contact being made.

The use of the individual embodiments for the interconnection arrangement20depends on the requirement and the application. However, it is obvious that the invention is not limited to the described examples, so that other embodiments of the interconnection arrangement20and of the stator10are also possible.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.