Patent Application
20230098997
The invention relates to a stator having a contact apparatus for contacting coils of a stator winding. The invention further relates to an electric motor, in particular an electronically commutated steering motor of a motor vehicle, having such a stator.
Motor vehicles nowadays usually have a number of adjusting parts, for example a steering system, a seat adjustment system, an actuatable lock, window lifter, an adjustable sunroof, which are adjustable or movable between different setting positions by means of an associated electromotive drive.
An electric motor, in particular brushless electric motor, as electric three-phase machine generally has a stator with a number of stator teeth, which are arranged for example in a star shape and support an electric rotary-field or stator winding in the form of individual coils, which are wound from an insulating wire. The coils are associated with their coil ends (winding wire ends) to individual strands or phases and are connected to one another in a predetermined way and are guided to phase connections to energize the rotary-field winding.
In the case of a brushless electric motor as a three-phase, electronically commutated three-phase machine, the stator has three phases and thus at least three phase conductors or phase windings, which are each suppled with electric current shifted in phase in order to generate a magnetic rotary field, in which a rotor that is usually provided with permanent magnets rotates. The phase ends of the phase windings are guided to a motor electronics unit for to control the electric motor. The coils of the rotary-field winding are connected here in a start circuit or in a delta circuit and electrically contacted with the three phase connections.
To guide and connect the coil ends, contact apparatuses in the form of interconnection systems or switch units are usual, which are fitted on an end face of the stator or of a stator assembly. Contact apparatuses of this kind are used in particular to electrically conductively connect the coil ends of the winding wire portions forming the coil windings, so that individual coil ends are electrically connected to one another (short-circuited) and therefore the coil or phase windings can be energized in series.
Contact apparatuses of this kind often have a number of integrated or overmolded conductor tracks or busbars as connection conductors for connection or contacting of the coil ends. When assembling the electric motor or busbars, the coil ends are contacted with the busbars so that coils associated with a common phase are connected to one another via the contacting apparatus. The coil ends are contacted with the busbars generally by means of an integrally bonded connection, for example by means of soldering or welding, in particular by means of laser welding.
Document DE 10 2010 039 335 A1 discloses a contact device of a stator of an electric motor, by means of which a number of coils arranged circumferentially of the stator are electrically contacted. The contact device has an annular contact support made of an electrically insulating material and also, for contacting the coils, electrically conductive conductor tracks, which are energized via axially protruding phase connections and are received in various planes lying parallel to the contact support plane.
It is conceivable that, by means of such a contact device (switch unit), which is arranged at an end face of a stator assembly with a stator main body supporting coils, not all coils are connected to one another. Due to the connection of the coils or their coil ends to the contact device, an at least two-phase (2-phase), preferably a three-phase (3-phase) electric motor is created. The contact device, which forms the interface between the stator and a motor electronics unit, has a number of connection elements (connection terminals) which generally corresponds to the number of phases.
A typical characteristic of the conductor tracks of the contact device, which is generally made of a material that is a good electrical conductor, preferably of copper or a copper alloy or of aluminum or an aluminum alloy, can be seen in the fact that they are laid over the shortest, often most intuitive path. Here, a predefined minimum distance between adjacent conductor tracks must not be undershot, whereby the electrical (ohmic) resistance is kept small (slight, low). The conductor track cross section in this case is usually constant within a conductor track or between the conductor tracks.
A disadvantage of this method of laying of the conductor tracks is that the symmetry of the (electrical) resistances measurable from the outside, in particular in the case of small coil resistances, may vary greatly, even if the coil resistances themselves are identical. This asymmetry may have a disadvantageous effect on the closed-loop and/or on the open-loop control of the electric motor by the electronics unit (motor electronics unit) and may generate an increased torque ripple and/or a high noise level.
The object of the invention is to describe a stator having a particularly suitable contact apparatus. In particular a torque ripple and/or a noise level is to be kept to a minimum by means of the contact apparatus. For this purpose, the greatest possible resistance symmetry of the phases is preferably to be produced. Furthermore, a particularly suitable electric motor having a stator of this kind is to be described.
The object is achieved in accordance with the invention by the features of claim 1 with regard to the stator and by the features of claim 10 in respect of the electric motor. Advantageous embodiments and developments are the subject matter of the dependent claims. The advantages and embodiments described in view of the stator are transferrable correspondingly also to the electric motor, and vice versa.
The stator has a stator main body, which extends along a stator axis and which supports a number of coils of a multi-phase winding, wherein each coil has two, in particular axially oriented, coil ends. The stator furthermore has a contact apparatus, which is arranged on an end face of the stator main body and which has a preferably annular interconnection housing that receives a number of busbars for interconnecting the coils and a number of phase connections, each of which is connected to one of the busbars. The stator winding is embodied in a suitably redundant manner, in particular with two lots of three phases.
Each phase of the stator winding is formed by at least one of the coils and at least one of the busbars as well as one of the phase connections, wherein the dimensions of the busbars are set in such a way that the electrical resistance of all of the phases of the stator winding is the same. The dimensions of the busbars are suitably set in such a way that the electrical resistance of the busbars is the same. For this purpose, the bar length and/or the bar cross section of the busbars is (are) advantageously set in such a way that the electrical resistances of the phases of the stator winding are the same. Each busbar expediently has at least one connection contact for contacting one of the coil ends.
With a suitable shape (geometry) of the busbar with a conductor track length or busbar length specified in respect of the particular resistance, it is also possible to bridge a distance, which by comparison with this length is small, between the contact points to be connected to this busbar, for example between the coil ends to be connected or those with a phase connection, by forming the corresponding busbar in an undulating, meandering or loop-like manner, for example. In other words, the corresponding busbar can be — even significantly — longer than the smallest distance between the contact points to be connected of the corresponding coils and/or the particular phase connection.
In an advantageous embodiment, the coils and their coil ends are arranged on the stator main body in such a way that a coil end of each of the coils is arranged on a radially inner circumference of the stator. In particular, with an arrangement of this kind of these coil ends, it is advantageously made possible that those busbars connecting the coils of a particular phase are the same for each of the phases.
In an advantageous embodiment, the coils are interconnected in a star circuit. To produce the star point of the star circuit, merely one individual busbar is used, which has three connection contacts and two busbar rail portions extending therebetween, which preferably have different portion lengths. The setting of the desired resistance symmetry can thus be simplified advantageously.
The invention is based on the consideration that an increased torque ripple and/or an increased noise level can be avoided if the electrical resistance of all phases of the stator winding or motor winding is the same. Since the electrical resistances of the coils involved in the stator winding are typically the same or identical, it has been found that the resistance symmetry can be optimized by adapting the resistances of the conductor tracks or busbars.
The resistances are generated here either by a change in cross section or by a change in length of all or certain busbars (conductor tracks). In this case, the busbars can have different cross sections from one another. The cross section can also vary along an individual busbar. Due to the change in length, for example due to an additional loop or a wave shape, the busbars (conductor tracks) are no longer necessarily laid over the shortest or most intuitive path. The cross sections can also vary here within an individual busbar.
A resistance symmetry of this kind can be produced in the case of electric motors having coils interconnected in a star circuit and in a delta circuit as well as in the case of electric motors having redundant windings, for example two three-phase stator windings (2 x 3 phases). Due to the very good resistance symmetry, electric motors of this kind can be controlled in a particularly exact manner and at the same time generate no or only minor torque ripples or noise.
In a further advantageous embodiment, the busbar to be connected to the phase connection has a joining end, which reaches through a corresponding, preferably rectangular recess of a connection portion of the phase connection. The busbar to be connected to the phase connection expediently has a joining end (fixing end), which reaches through the corresponding recess of the connection portion of the phase connection. The joining end of the busbar is suitably deformed or re-shaped in the connection (joint) to the phase connection, thus forming a, for example mushroom-head-shaped, fixing head overlapping the recess at least in some regions. This connection is particularly preferably produced as a welded connection, expediently by means of laser welding. The phase connections are suitably formed as insulation displacement contacts.
In the case of electric motors with redundant stator winding, i.e. in the case of redundant motors with a plurality of sub-systems accordingly, in which only one sub-system is controlled, the deviation of the current from the other sub-system in motor operation is low, which in turn improves the controllability. In addition, the (direct) current of the energized stator winding or the phases can be estimated more precisely.
In a preferred application, the above-described stator is part of an electric motor of a motor vehicle. The electric motor according to the invention is preferably a steering motor here, for example inclusive of a gearing, for the steering of the motor vehicle.
Exemplary embodiments of the invention will be explained in further detail hereinafter with reference to a drawing, in which:
In the schematic illustration, the stator winding 3 is of three-phase configuration with three (motor) phases U, V, W. Each phase U, V, W is formed from a phase winding, which in the exemplary embodiment is formed by an interconnection of two coils (coil winding) 7 of the stator winding 3. The phases U, V, W are interconnected in this exemplary embodiment in a star circuit with a star point B.
The coils 7 are wound in the exemplary embodiment on insulating winding supports or coil supports 9 and are fitted with the latter onto the stator teeth of the stator main body 8. Each of the frame-like winding supports 9 in this case supports a coil 7 as part of the stator winding 3. The coils 7 each have two axially directed coil ends 10. The coils and their coil ends are provided in
The coil ends 10 of the coils 7 are interconnected by means of the contact apparatus 5 fitted on an end face of the stator 2 to form the three-phase (3-phase) stator winding or rotary-field winding 3, which is redundant in this exemplary embodiment. In electromotive operation, the energized windings of the stator winding 3 each generate a stator-side magnetic field, which interacts with permanent magnets of a rotor of the brushless electric motor 1 rotating about the central stator or motor axis A. By means of the motor electronics unit 6, it is possible to switch to other phases U, V, W for energization of the latter, for example if individual phases U, V, W drop out as the result of a defect.
The contact apparatus 5 has a circular ring-shaped interconnection housing 11 made of electrically insulating material. The coil ends 10 of the coils 7 are guided through radially inwardly arranged, axial through-openings 12 of the interconnection housing 11 and are contacted on the upper side of the interconnection housing 1 to contact lugs 13 for interconnection. The through-openings 12 and contact lugs 13 are provided in the figures with reference signs merely by way of example.
The contact apparatus 5 is fastened or fastenable to the stator main body 8 in a form-locking and/or force-locking engaged manner by means of axial detent tongues 14 of the interconnection housing 11. The detent tongues 14 are distributed here on the outer circumference and are arranged on the (lower) side of the interconnection housing 11 facing the stator main body 8. The stator main body 8 in this case has, on its outer circumference, axially running grooves 15 in which the detent tongues 14 engage in a clamped manner for fastening. The contact apparatus 5 arranged on the corresponding end face of the stator 2 is releasably latched or fastened in a clamped manner to the stator main body 8.
As can be seen in conjunction with
The six phase connections 4 in the exemplary embodiment provide three connection pairs for the phases U, V, W of the three-phase stator winding or rotary-field winding 3 formed by the coils 7 and interconnection thereof. Each of the connection pairs with the three phases U, V, W and the associated busbars 16 forms one of two redundant sub-systems of the stator winding 3.
The axially directed joining ends 17 are provided as contact points for the connection to the associated phase connections 4 and are molded integrally, that is to say in one piece or monolithically, onto the busbars 16. The axially directed contact lugs 13 as contact points for contacting or electrically conductively connecting the associated coil end 10 are also integral constituents of the busbars 16. The contact lugs 13 are embodied in particular as welding lugs for a welded connection, preferably for a laser welded connection, to the coil ends 10, which in particular are stripped. The busbars 16 with their joining ends 17 and contact lugs 13 are embodied here for example as stamped and bent parts made of a copper material.
The phase contacts 4 are embodied in this embodiment as approximately rectangular contact lugs in the form of a stamped and bent part. The long sides of the particular phase connection 4 are oriented here in the axial direction A, wherein the narrow sides are oriented for example radially. The particular phase connection 4 protrudes axially upward at the stator end face supporting the interconnection housing 11. For support and stabilization, the phase contact 4 sits in the assembled or joined state of the electric motor 1 in a holding receptacle of the interconnection housing 11 of the contact apparatus referred hereinafter as a support portion 18. The phase connections 4 are provided as insulation displacement contacts or connection and for this purpose are provided on the free end side with a receiving slot 19 for a blade contact of the motor electronics unit 6.
As can be seen relatively clearly from
In the shown joined stated, a form-locking and integrally bonded connection 23, in particular a welded connection, is produced between the joining end 17 of the busbar 16 and the connection portion 4b of the phase connection 4, expediently by means of laser welding. This is carried out when the joint is produced and the components (busbars 16 and/or phase connections 4) of the contact apparatus 5 are overmolded, that is to say the interconnection housing 11 is completed. This housing then has a preferably planar, annular base portion 21. In this state, the joining end 17 protrudes through an opening 22 in the interconnection housing 11 to the upper side of the latter formed by the base portion 21. The joining end 17 or tapering 20 thereof of the busbar 16 is deformed in the connection produced by means of laser welding (form-locking and integrally bonded joint) to the phase connection 4. These connections are accessible following the overmolding of the corresponding portions of the busbars 16.
The connection portions 4b of the phase connections 4 run in the circumferential direction or tangentially based on the annular base portion 21 of the connection housing 11, whereas the joining ends 17 of the busbars 16 to be connected to the phase connections 4 are oriented axially. In this way, the joining ends 17 of the busbars reach through the recesses 20 in the phase connections. The contact lugs 13 of the busbars 16 are positioned in a radially inner region of the interconnection housing 11, opposite the connection portions 4b of the phase connections 4 and their connection or contact points to the busbars 16.
Hereinafter, the phase connections, the coils and coil ends thereof as well as the busbars are provided with indexed letters instead of the numbers (4, 7, 10, 16) used in
In the left half of
Specifically, in the case of the sub-system shown on the left in
The fourth coil SP4 associated with the second phase V is connected with its other coil end SP42 to a fourth busbar S4, which is connected to a coil end SP32 of a third coil SP3, which with the fourth coil SP4 forms the phase V. The other coil end SP31 of the third coil SP3 is connected to a fifth busbar S5, which is in turn connected to the connection portion 4b of the phase connection 4, designated here by P2, of the phase V in the described form-locking and integrally bonded joint.
The fifth coil SP5 associated with the third phase W is connected by its other coil end SP52 to a sixth busbar S6. which is connected to a coil end SP62 of a sixth coil SP6, which with the fifth coil SP5 forms the phase W. The other coil end SP61 of the sixth coil SP6 is connected to a seventh busbar S7, which is in turn connected to the connection portion 4b of the phase connection 4, designated here by P3, of the phase W in the described form-locking and integrally bonded joint.
The dimensions of the busbars S1, S4 and S6, which connect the coil pairs SP12, SP34 and SP56 of the phases U, V and W respectively, are the same in respect of their dimensions and can thus be provided advantageously as identical parts. The dimensions of the busbars S2, S3, S5 and S7 are different, wherein their bar length and/or bar cross section is set in such a way that the electrical resistances R of all three phases U, V, W are the same and thus the electrical resistance of the first sub-system of the stator winding 3, said sub-system being embodied in a star circuit by means of the contact apparatus 5, is symmetrical.
The symmetry (resistance symmetry) can be specified advantageously as a quotient of the difference of the maximum and minimum resistance between two phases and the mean resistance between the phases (symmetry = (maximum resistance between two phases — minimum resistance between two phases)/mean resistance between the phases). The value of the symmetry is advantageously <1 %.
This resistance symmetry is also set in the sub-system shown on the right in
Specifically, in the sub-system shown in the right in
The coil SP10 associated with the second phase V is connected by its other coil end to an eleventh busbar S11, which is connected to a coil end of a ninth coil SP9, which with the coil SP10 forms the phase V. The other coil end of the coil SP9 is connected to a twelfth busbar S12, which is in turn connection to the connection portion 4b of the phase connection 4, designated here by P5, of the phase V in the described form-locking and integrally bonded joint.
The coil SP11 associated with the third phase W is connected by its other coil end to a thirteenth busbar S13, which is connected to a coil end of a twelfth coil SP12, which with the coil SP11 forms the phase W. The other coil end of the coil SP12 is connected to a fourteenth busbar S14, which is in turn connected to the connection portion 4b of the phase connection 4, designated here by P6, of the phase W in the described form-locking and integrally bonded joint.
The dimensions of the busbars S8, S11 and S13 are again the same in respect of their dimensions and those of the busbars S1, S4 and S6. The dimensions of the busbars S9, S10, S12 and S14 are different, wherein their bar length and/or bar cross section is again set in such a way that the electrical resistances R of all three phases U, V, W are the same and thus the electrical resistance of the second sub-system of the stator winding, said sub-system being embodied in a star circuit by means of the contact apparatus 5, is symmetrical. The dimensions of the busbars S2 and S9 are the same in the exemplary embodiment, whereas the dimensions of the busbars S10, S12 and S14 are different from one another and also in relation to the busbars S3, S5 and S7.
As can be seen for example with reference to the busbars S7 and S12, their busbar length is only small in comparison to the distance between the coil end SP61 and the phase connection P3 or between the corresponding coil end of the coil SP10 and the phase connection P5, and therefore a suitable shape (geometry) of the busbars S7 and S12 is selected by shaping the corresponding busbars S7 and S12 in a loop-like or undulating or meandering manner in order to provide the necessary electrical resistance.
The invention is not limited to the above-described exemplary embodiment. Rather, other variants of the invention can be derived herefrom by a person skilled in the art, without departing from the subject matter of the invention. In particular, all individual features described in conjunction with the exemplary embodiments can also be combined with one another in other ways without departing from the subject matter of the invention.
In addition, the invention can be used not only in the application specifically presented, but also in a similar embodiments in other motor vehicle applications, for example in door and tailgate systems, in window lifters, in vehicle locks, in adjustable seat and systems and interior systems, as well as in electric drives, control systems, sensors and their arrangement in the vehicle.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 200 839.6 | Jan 2020 | DE | national |
| 10 2020 202 578.9 | Feb 2020 | DE | national |
| 10 2020 203 870.8 | Mar 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/051166 | 1/20/2021 | WO |
