Connection device for an electric machine, electric machine and method for manufacturing a connection device for an electric machine

Abstract

The invention provides a connection element for a multiphase electric machine. The connection element is designed to be so simple that it can be manufactured using a basic injection molding process in which several busbar elements are overmolded. In this process, the injection molded part that secures the busbar elements also integrates a filter element, for example, a ferrite core. This allows for a very compact design for a connection element with simultaneous filtering function.

Description

Technical FieldThe present invention relates to a connection device for an electric machine, in particular a polyphase electric machine. The present invention further relates to an electric machine having such a connection device. Furthermore, the present invention relates to a method for producing a connection device for an electric machine.Prior ArtFully or at least partially electrically driven vehicles have an electric drive system in which an electric machine is supplied with electrical energy by means of an electric power converter, in particular an inverter (inverter), in order to drive the vehicle. Optionally, when decelerating the vehicle in a so-called recuperation mode, the electric machine can convert kinetic energy of the vehicle into electrical energy. The alternating voltage provided by the electric machine can be converted by means of the power converter into an electrical voltage which is suitable for charging an electrical energy store, for example a traction battery in the vehicle. Due to the high electrical powers occurring in this case, the electrical power converter and the electrical machine must be reliably connected to one another in this case.In Publication 10 2018 201 819 A1, an electric vehicle axle device is described. This vehicle axle device comprises power electronics with an inverter, an electric motor and a transmission.Disclosure of the InventionThe present invention discloses a connecting device for an electric machine, an electric machine and a method for producing a connecting device for an electric machine having the features of the independent claims. Further advantageous embodiments are the subject matter of the dependent claims.Accordingly, the following is provided:A connection device for a polyphase electric machine having a plurality of busbar elements, a filter element and an electrically insulating injection-molded element. Here, a busbar element is provided for each electrical phase of the electrical machine. The plurality of bus bar members are each surrounded by the injection molded member at predetermined positions. As a result, the plurality of busbar elements are fixed. Furthermore, each busbar element is configured to be electrically coupled at a first end to a stator terminal of the electric machine. Furthermore, each busbar element is designed to be electrically coupled at a second end to a connection element of an inverter. The filter element is embedded in the injection-molded element. The filter element encloses the plurality of busbar elements. The filter element is thus an integral component of the injection-molded element, which encloses the busbar elements.Furthermore, the following is provided:An electric machine having a housing and a connection device according to the invention. The housing is configured to receive a stator and a rotor of the electric machine. The housing further has an opening. In this case, a busbar element is electrically coupled in each case to a corresponding terminal for a phase of the stator of the electric machine.Finally, the following is provided:A method for producing a connection element for an electric machine. The method comprises a step of providing a plurality of busbar elements. Here, a busbar element is provided for each electrical phase of the electrical machine. The method further comprises a step of providing a filter element with a ferrite core. Furthermore, the method comprises a step for arranging the plurality of busbar elements and the filter element in an injection molding device. The method further comprises a step of overmolding the filter element and the plurality of busbar elements with an electrically insulating material. In this way, an electrically insulating injection-molded element is formed around the busbar elements. Each busbar element is configured to be electrically coupled at a first end to a stator terminal of the electric machine and to be electrically coupled at a second end to a terminal element of an inverter.Advantages of the InventionThe present invention is based on the finding that a suitable connection must be provided for the connection of a polyphase electric machine to a current source, such as an electric power converter (inverter), for example. In addition, a separate filter element, for example in the form of a ferrite core, can be provided to reduce the electromagnetic interference. The attachment of such an additional filter element requires additional working steps. Moreover, such an additional filter element requires a relatively large installation space.It is therefore an idea of the present invention to provide a concept for a connection element for connecting the electric machine to a power converter, which can simultaneously also contain the required components for filtering for suppressing electromagnetic interference.For this purpose, it is provided to equip a connection element for contacting the electric machine with a power converter simultaneously with a suitable filter element for suppressing electromagnetic interference. By integrating such a filter element into an injection-molded carbon black component, which at the same time also ensures the mechanical stability of the connection element of the latter, a very compact and efficient design can be realized. Since the filter element is integrated in the injection-molded element, a corresponding external component can be dispensed with. This reduces the installation space required for this purpose. Moreover, such an integral configuration also reliably ensures that the filter component is not forgotten during assembly of the electric drive system.According to an embodiment, the filter element may comprise a ferrite core. Ferrite cores are very well suited for filtering electromagnetic influences and have already proven themselves in the past for such applications. Moreover, they are also well suited for being integrated into an injection molding component.According to one embodiment, each busbar element has a cutout in a region of the enclosing injection-molded element for fixing the busbar element in the injection-molded element. For example, grooves, depressions, holes or the like can be provided in the busbar elements, into which grooves the injection-molded material penetrates during the production of the injection-molded element and thus prevents displacement, movement or the like of the busbar elements.According to one embodiment, the injection molding element comprises a plurality of injection molded bushings. The individual sockets can be designed in such a way that the connection element is screwed to a housing of the electric machine by means of a screw. For example, such bushings can likewise be introduced into the injection mold and injection molded during the production of the injection molding element. Bushings can be made of any suitable material, for example a metal or the like.According to one embodiment, the injection-molded element has a circumferential cutout. This cutout can be designed to accommodate a sealing element for sealing an area between the connection device and a housing of the electric machine. By means of such a recess, a particularly good seal between the injection-molded element and the housing can be realized.According to one embodiment, a sealing element for sealing the region between the connection device and the housing of the electric machine is provided on the injection-molded element. The sealing element can be made of an elastomer or the like, for example. For example, the sealing element can be a circumferential rubber seal.According to one embodiment, the busbar elements each comprise a holding section. This holding section can be configured to fix the busbar element during an injection molding process for attaching the injection molding element. Such a holding section can be provided on a side of the busbar elements which points in the direction of the connection region for the power converter. Additionally or alternatively, such a holding section can also be provided on the opposite side of the busbar elements, which points from the injection-molded element in the direction of the connection for the stator windings.The above embodiments and developments can be combined with one another as desired, insofar as appropriate. Further embodiments, developments and implementations of the invention also include combinations of features of the invention described above or below with respect to the exemplary embodiments, which combinations are not explicitly mentioned. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.Brief Description of the DrawingsFurther features and advantages of the invention are explained below with reference to the figures. The following are shown: FIG. 1 : shows a schematic illustration of a cross section through a connection device according to one embodiment; FIG. 2 : shows a schematic plan view of a connection device according to one embodiment; FIG. 3 : shows a schematic illustration of an electric machine having a connection device according to one embodiment; and FIG. 4 : shows a flow chart on which a method for producing a connection device according to one embodiment is based.DESCRIPTION OF EMBODIMENTSFIG. 1 shows a schematic illustration of a cross section through a connection device 1 for an electric machine according to one embodiment. The terminal device 1 includes a plurality of bus bar members 10- i. The number of busbar elements 10- iis generally equal to the number of electrical phases in the electrical machine. In addition to the usual number of three busbar elements 10- iillustrated here, however, embodiments with a different number of busbar elements are also possible in principle.The individual busbar elements 10- imay be formed in a first region 11 illustrated here above in such a way that they can be connected to an electrical power converter for the electrical machine. If necessary, the shape can be adapted in such a way that direct contacting with the power converter is possible.In an opposite region 12, illustrated here below, the individual busbar elements 10- imay be formed in such a way that they can be connected to the connections for the phase windings on the stator of the electric machine. In this case, too, the length, shape, connection region, etc. can be adapted in accordance with the requirements for the connection.The individual busbar elements 10- iare made of an electrically conductive material, for example copper or the like. In this case, no special coating of the material for the busbar elements 10- iis required, if appropriate.In a central region, the busbar elements 10- iare fixed by means of an injection-molded element 20. The injection-molded element 20 is electrically insulating. In this case, the injection-molded element 20 ensures that the busbar elements 10- iare at their desired position and sufficient insulation is present between the individual busbar elements 10- i.For better fixing, recesses 13 can be provided on the busbar elements 10- i. These recesses 13 can be, as shown in FIG. 1, for example, notches or the like. In principle, however, other suitable configurations are also possible which ensure that the busbar elements 10- iare held reliably by the injection-molded element 20.For producing the connection element 1, the individual busbar elements 10- imay be inserted, for example, into a mold of an injection molding device. In order to fix the busbar elements 10- iduring the injection molding process, a holding region 14 a, 14 bmay be provided between the position of the injection molding element 20 and the connection regions 11 or 12 for the power converter or the stator windings. At this neck region 14 a, 14 b, the busbar elements 10- imay be fixed during the injection molding process by a suitable holding device until the injection molding material has cured.Furthermore, a filter element 50 is provided in the connection device 1, which filter element encloses the busbar elements 10- i. For example, a ferrite core may be provided as filter element 50. Such a filter element 50 can minimize electromagnetic interference effects. The filter element 50 can likewise be introduced into the injection mold during the production of the connection device 1. Thus, during the injection molding process, the injection molding material can surround and fix the bus bar members 10- i, and also the filter member 50. As a result, the filter element 50 becomes an integral component of the injection-molded element 20 and thus also of the connection element 1.Furthermore, one or more sockets 30 can be provided in the connection device 1. These bushings can be openings through which a screw can be passed in order to screw the connection element 1 to a housing of the electric machine. For example, suitable bushing elements made of metal or another suitable material can also be provided for the bushings, which are likewise insert molded during the production of the injection molding element 20.Furthermore, a recess 21 can be provided in the injection-molded element 20, into which a sealing element 40 can be introduced. This recess can be, for example, a completely encircling recess into which a sealing element 40, such as a rubber ring or the like, is introduced. In principle, any suitable sealing material, for example an elastomer or the like, can be used as sealing element 40. In addition to the embodiment shown in FIG. 1, in which the sealing element 40 is provided on the lateral edge of the connection device 1, it is also possible for the sealing element 40 and thus also the corresponding cutout 21 to be provided on a side which points in the direction of the connection regions 12 for the stator windings.FIG. 2 shows a schematic illustration of a plan view of a connection device 1 according to the embodiment. The components shown here for the busbar elements 10- i, the injection-molded element 20, the sockets 30, etc. correspond to the corresponding components according to FIG. 1.The configuration of the injection-molded element 20 is designed in accordance with an opening into which the connection element 1 on the housing of an electric machine is introduced. The injection-molded element 20 can thus completely close this opening. For fastening the connection element 1 to the housing of the electric machine, the injection-molded element 20 can be screwed to the housing at the sockets 30. If, for example, self-locking screws are used, a secure and reliable locking can be ensured. In this case, it is possible to dispense with securing by means of interlock or the like, if appropriate.As can be further seen in FIG. 2, the filter element 50 encloses the busbar elements 10- iin an annular manner. The filter element 50 is preferably completely surrounded by the material of the injection-molded element 20.FIG. 3 shows a schematic illustration of a cross section for illustrating the connection of an electric machine to a connection element 1 according to one embodiment. The electric machine comprises, among other things, a stator 2 with corresponding connections 2 cfor the stator windings. The internal components of the electric machine are surrounded by a housing 2 a. An opening 2b is provided on this housing 2. The connection device 1 according to the invention can be introduced into this opening. Then, the terminal portions 12 of the bus bar members 10- imay be connected, for example, screwed, to the terminals 2 cfor the stator windings. At the opposite ends of the bus bar elements 10- i, the terminal portions 11 may be connected to an electric power converter 4 or another voltage source. As already described above, the connection element 1 can be screwed to the housing 2 aat the sockets 30. A secure and reliable seal is achieved by the sealing element 40.FIG. 4 shows a flow chart on which a method for producing a connection element 1 according to one specific embodiment is based. The connection element 1 can be the connection element 1 described above. Accordingly, the following method can have any steps which may be required for producing such a connection element 1. Analogously, a connection element 1 described above can also have any desired components, as can be produced during the production of the method described below.In a step S 1, a plurality of bus bar members 10- iis provided. In this case, a busbar element 10- iis provided for each electrical phase of the electrical machine. In step S 2, a filter element 50, for example with a ferrite core, is provided. Subsequently, in step S 3, the filter element 50 and the plurality of busbar elements 10- iare arranged in an injection molding device. Subsequently, in step S 4, an electrically insulating material is applied by injection molding around the filter element 50 and the plurality of busbar elements 10- i. An electrically insulating injection-molded element 20 is thereby formed.The plurality of busbar elements 10- imay each be formed from an uncoated electrically conductive material. Furthermore, each busbar element 10- iis designed to be electrically coupled at a first end 11 to a stator terminal 2 cof the electric machine and to be electrically coupled at a second end 12 to a terminal element of an inverter 4.In a further step, a circumferential sealing element 40 can be attached to the injection molding element 20. This sealing element 40 can be mounted, for example, in a circumferential recess 21 of the injection-molded element 20. The attachment can be automated as well as manual. As already explained above, the sealing element 40 and the cutout 21 adapted thereto can be provided either in time or on a surface facing the housingIn summary, the present invention relates to a connection element for a polyphase electric machine. The connection element is configured in such a simple manner that it can be realized by means of a simple injection molding process, in which a plurality of busbar elements are injection molded. Here, in the injection molding element that fixes the busbar elements, a filter element, for example a ferrite core, is additionally integrated. In this way, a very compact design for a connection element with a simultaneous filter function can be realized.

Claims

A terminal device (1) for a polyphase electric machine, comprising: a plurality of bus bar elements (10-i), wherein a bus bar element (10-i) is provided for each electric phase of the electric machine; an electrically insulating injection molding element (20) enclosing the plurality of bus bar elements (10-i) respectively at predetermined positions and fixing the plurality of bus bar elements (10-i) thereby; and a filter element (50) embedded in the injection molding element (20) and enclosing the plurality of bus bar elements (10-i), wherein each bus bar element (10-i) is configured to be electrically coupled to a stator terminal (2c) of the electric machine respectively at a first end (12) and to be electrically coupled to a terminal element of an inverter (4) at a second end (11).The connection device (1) according to claim 1, wherein the filter element (50) comprises a ferrite core.Connection device (1) according to claim 1 or 2, wherein each busbar element (10-i) has a cutout (13) in a region of the enclosing injection-molded element for fixing the busbar element (10-i) in the injection-molded element (20).Connection device (1) according to one of Claims 1 to 3, wherein the injection-moulded element (20) comprises a plurality of injection-moulded bushes (30), wherein the bushes (30) are configured to screw the connection element to a housing (2a) of the electric machine by means of a screw.Connection device (1) according to one of Claims 1 to 4, wherein the injection-moulding element (20) has a circumferential cutout (21) which is designed to receive a sealing element (40) for sealing a region between the connection device (1) and a housing (2a) of the electric machine.Connection device (1) according to Claim 5, having a sealing element (40) for sealing the region between the connection device (1) and the housing (2a) of the electric machine.The connection device (1) according to any one of claims 1 to 6, wherein the busbar elements (10-i) each comprise a holding portion (14a, 14b) configured to fix the busbar element (10-i) during an injection molding process for attaching the injection molding element (20).An electric machine, comprising: a housing (2a) configured to receive a stator (2) and a rotor of the electric machine; and a connection device (1) according to any one of claims 1 to 7, wherein the housing (2a) has an opening (2b) for the connection element (1), and wherein a busbar element (10-i) is electrically coupled to a corresponding phase of the stator (2) of the electric machine, respectively.Electric machine according to Claim 8, wherein the connection element (1) is screwed to the housing (2a) of the electric machine by means of self-securing screws.Method for producing a connection element (1) for an electric machine, having the steps: providing (S 1) a plurality of busbar elements (10-i), wherein a busbar element (10-i) is provided for each electrical phase of the electric machine; providing (S 2) a filter element (50) having a ferrite core; arranging (S 3) the plurality of busbar elements (10-i) and the filter element (50) in an injection moulding device; and injection molding (S 4) the plurality of busbar elements (10-i) and the filter element (50) with an electrically insulating material in order to form an electrically insulating injection molding element (20), wherein each busbar element (10-i) is configured to be electrically coupled at a first end (12) to a stator terminal (2c) of the electric machine and to be electrically coupled at a second end (11) to a terminal element of an inverter (4), respectively.

Images