Stator and method for manufacturing a stator of an electric machine

Abstract

A method for manufacturing a stator (20) for an electric machine is provided, the method comprising: providing the stator (20) having at least one stator groove (22) delimited by two stator teeth; introducing electrical conductors (30) into the at least one stator groove (22), wherein at least one conductor (30) has an expandable coating (25) locally applied on its surface; and activating the expandable coating (25) to expand the expandable coating (25), thereby fixing the conductors (30) in the stator groove (22). In addition, a stator (20) manufactured according to the method of the present invention is provided.

Description

Technical Field

[0001] The invention relates to a method for producing a stator of an electric machine and to a stator produced according to the method. Background Art

[0002] Electric machines use a rotor and a stator to convert electrical power into mechanical power (electric motor) and vice versa (generator) by means of electromagnetic induction. Although modern electric machines used in today's electric vehicles have extremely high efficiencies of well over 90%, power losses due to heat loss on the conductors through which the current flows during operation are unavoidable and must be dissipated. If the amount of heat loss dissipated is insufficient, this has a negative impact on the power efficiency and service life of the electric machine. In high-power machines with a power of several hundred kilowatts, the heat loss generated at high power is usually dissipated with the help of water cooling devices.

[0003] In principle, there are two approaches for cooling the electric machine, which can also be used together if necessary. Thus, jacket cooling can be used, in which the heat is conducted from the conductor in the groove via the stator to the flow channel on the outer diameter of the stator. Additionally or alternatively, the cooling medium can flow directly through the groove, and the heat is thus absorbed directly at the location of generation (i.e. at the conductor) and discharged from there. This approach is referred to as direct cooling.

[0004] In electric motors with direct cooling of the windings, the flow cross section for the cooling medium adjacent to the windings must remain unobstructed. For this reason, impregnation or casting with resin, which is usually used to fix the conductors arranged in the grooves, is abandoned so that they cannot move relative to each other. In order to counteract undesired relative movements (conductor / conductor or conductor / lamina pack) which could lead to damage to the main insulation on the conductors and thus to failure of the electric machine, the individual conductors or conductor bars must be mechanically fixed / clamped in some other way.

[0005] For example, a method for fixing conductors for stators is known from document EP 2 475 076 A1, which is based on an expandable coating. That is, the document discloses a stator for an electric machine, which has a stator core with a plurality of stator grooves, wherein electrical conductors are arranged in the stator grooves. The conductors are wrapped with an expandable band. After the conductors are inserted into the grooves, the expandable band expands due to the heat input.

[0006] The conventional structure in the stator grooves provides groove backing paper, conductors and usually resin impregnation or complete casting with resin. In most cases, impregnation is carried out as the last manufacturing step of the stator after the steps of pinning, expansion, bending and contacting with the conductors (if plug-in coils are used, which is increasingly common nowadays). The resin can be introduced onto the conductors, for example, by dripping, dipping, padding, vacuum casting or over-injection. The resin here particularly assumes the function of fixing the windings. Summary of the invention

[0007] It can be seen that the object of the invention is to provide a simplified method for producing a stator and a correspondingly produced stator which has an effective cooling effect for operation at high power, in particular permanently.

[0008] This object is achieved by a method for producing a stator of an electric machine and a correspondingly produced stator. In addition, there are further preferred embodiments.

[0009] The method for manufacturing a stator of an electric machine according to the invention comprises providing a stator having at least one stator groove, the at least one stator groove being delimited by two stator teeth. The stator may have a lamination pack and (as is common in electric machines, in particular electric vehicles) a plurality of grooves (e.g. 54 grooves), each of which is separated by a tooth. Without limiting generality, the following description is directed to the stator grooves in the stator, as this is sufficient to illustrate the invention.

[0010] The method according to the invention further comprises: introducing an electrical conductor into the at least one stator groove, wherein at least one conductor has a swellable coating applied locally on its surface. The fact that at least one conductor arranged in the groove has a locally formed coating can mean that: in a plurality of conductors (which extend through the groove), for example in 25% of the conductors, or in 50% or more of the conductors (for example in 75% of the conductors), in almost all of the conductors or in all of the conductors, this is the case. The conductor can be a conductor bar.

[0011] The local, expandable coating arranged on the surface of the at least one conductor refers to a coating that is not arranged on the entire surface of the elongated section of the conductor, but only covers a portion of this surface. In this regard, it can be related to a structured coating of the conductor with an expandable coating, because the coating is not uniformly, but rather unevenly arranged on the surface of the conductor to the greatest extent, in that some surface portions are coated and other surface portions are not coated when viewed along the elongated section of the conductor. The structured coating can exist in a predetermined pattern, such as a pattern repeated along the length of the conductor. The elongated surface section of the conductor refers to the entire surface of the conductor between the starting point and the end point along the longitudinal axis of the conductor. The distance between the starting point and the end point can, for example, roughly correspond to the length of the stator groove. According to the present invention, the local design of the coating on the conductor can especially relate to an elongated surface section, which is arranged in this groove after the conductor is inserted into the groove. Therefore, the length of the elongated section can roughly correspond to the length of the stator groove. The regions of the conductor which in each case project from the recess at the end face and the bottom face can, but do not necessarily have to, have the same local coating of similar design.

[0012] An expandable coating is a coating that can be activated and thus increases in volume, but preferably not necessarily initially in a direction substantially perpendicular to the surface on which it is arranged. The expandable coating can be activated in different ways (e.g. thermally, chemically, electromagnetically or mechanically). The volume increase of the expandable coating in the (permanently) activated state can be up to 100%. The activation of the expandable coating (which has been arranged "in situ", i.e. on the surface of at least one conductor) causes its volume to increase. This process can be called "in situ" impregnation, based on the impregnation process in the prior art by which the conductor is fixed. The expandable coating can be realized with the help of different materials. Polymer materials, such as expandable polymer foams, silicones, thermoplastics or thermosetting foams (especially epoxy resins) can be used as exemplary options.

[0013] Finally, the method according to the invention comprises activating the expandable coating so as to expand the expandable coating, thereby fixing the conductors in the stator grooves.

[0014] The method according to the invention is characterized in that at the end of the stator production chain, instead of the impregnation that is usually carried out later in the prior art to fix the winding, at least one conductor used to construct the stator has a local, expandable coating. The expandable coating is characterized by (as already described) an increase in volume when it is activated. The increase in volume causes the conductor (conductor bar) to be close to the stator lamellae and thus clamped from the outside. By only partially coating at least one conductor, preferably a plurality or several conductors, on the area arranged in the groove, a flow channel is formed in the stator groove. A cooling fluid can be guided through the flow channel by means of a regulated pressure difference, thereby enabling direct cooling.

[0015] Many advantages can be attributed to the manufacturing method according to the invention. On the one hand, the service life of the stator can be extended by preventing or at least significantly reducing the scratching friction between the conductor and its main insulation. In addition, direct cooling of the conductor has a positive effect on the service life of the stator, especially when a plurality of conductors in the groove, for example a sufficiently large number of conductors or even all conductors, have the described local coating, so that in principle each conductor can be directly cooled.

[0016] Another advantage can be seen in that by omitting the impregnation of the conductors, a production step is omitted and the production method is thus simplified. As a result, cheaper and less complex equipment technology can be used to produce the stator according to the production method of the invention.

[0017] Furthermore, the value chain is thereby optimized, as the coating of the conductors, which is carried out instead of the dipping method, is returned to the beginning of the production chain.

[0018] Yet another advantage can be seen in that the winding can be fixed in the groove already before the following manufacturing steps (such as expansion, twisting and contacting). Thus, these manufacturing steps are performed on the conductor that has already been fixed, which simplifies component handling.

[0019] In other embodiments of the manufacturing method, the expandable coating may be activated by heat input.

[0020] In other embodiments of the manufacturing method, after expansion of the coating has been achieved, at least one through-going fluid connection (flow channel) can extend through the stator groove, the at least one fluid connection being formed by an area of ​​the surface of the at least one conductor that is not covered by the coating. To this end, the coating can be arranged locally in a corresponding structure or in a corresponding pattern on the surface in the (associated) elongated area of ​​the conductor, so that the area of ​​the conductor surface that is not coated along the length of the conductor provides at least one flow channel.

[0021] In a further embodiment of the manufacturing method, the manufacturing method may further comprise: providing conductors for forming a winding of the stator, and coating at least one conductor with an expandable coating. In this case, the coating can be applied to the surface of the conductor in principle in two ways, i.e. i) partially or ii) completely, wherein the coating is subsequently partially removed in the latter case to achieve the partial coating of the conductor according to the invention.

[0022] In a further embodiment of the production method, the expandable coating applied locally on the surface of at least one conductor can be structured so that between the regions of the conductor that protrude from the stator after the conductors are inserted into the stator grooves there is at least one continuous path extending on the uncoated surface of the conductor. Each such path provides a flow channel in the finished state of the stator.

[0023] In other embodiments of the manufacturing method, the local coating can be arranged on the surface of the at least one conductor in the form of a spiral step-like structure. Therefore, in this embodiment of the local coating of the conductor, the cooling fluid channel extends around the conductor in a corresponding spiral step-like manner.

[0024] In other embodiments of the manufacturing method, the local coating can be arranged in the form of a plurality of separate layers on the surface of the at least one conductor, so that a continuous path extending on the uncoated surface of the conductor is present between regions of the conductor that extend from the stator and beyond the stator grooves after the conductors are inserted into the stator grooves.

[0025] According to other embodiments, a stator for an electric machine is also provided, the stator having at least one stator groove, the at least one stator groove being delimited by two stator teeth. The stator also has electrical conductors extending in the at least one stator groove, wherein the conductors are fixed in the stator groove and the surface of at least one conductor arranged in the stator groove is partially covered by an expandable coating. As defined above, the surface of the conductor refers to the associated full surface along the elongated area of ​​the conductor. The stator can be manufactured in particular by means of the method according to the invention described herein.

[0026] In other embodiments of the stator, the stator may have at least one fluid connection extending through the at least one stator groove, wherein the fluid connection is formed by a region of the surface of the at least one conductor which is not covered by the coating.

[0027] According to other embodiments, there is also provided the use of at least one conductor partially coated with an expandable material to form a winding of a stator, wherein the local coating is structured so that the uncoated areas of the conductor surface are arranged so that at least one path extends through these areas, and the at least one path connects two areas spaced apart from each other in the elongated direction of the conductor. Stated another way, the uncoated areas of the conductor surface are arranged so that they form at least one channel, and the at least one channel connects two areas spaced apart from each other in the elongated direction of the conductor. The channel does not necessarily have to be dedicated and / or straight here, but can have branches and / or branches. It is important that, from a topological point of view, there is at least one connection between two areas spaced apart from each other on the surface of the conductor in the elongated direction of the conductor, and the connection extends on the uncoated surface of the conductor.

[0028] The features mentioned above and those still to be explained below can be used not only in the respectively stated combination but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further advantages and embodiments of the invention are apparent from the description and the drawings.

[0030] Figure 1 A flow chart is shown in which an exemplary embodiment of the method according to the invention is illustrated.

[0031] Figure 2A and Figure 2B Simplified illustrations of a stator manufactured using the method according to the invention are shown, each showing a simplified illustration before and after activation of a localized, expandable coating.

[0032] Figure 3A and Figure 3B Two exemplary conductors are shown which can be used within the scope of the method according to the invention to form a winding of a stator. DETAILED DESCRIPTION

[0033] exist Figure 1 In the flow chart shown in , an embodiment of the method according to the invention is shown. In a first step 10, the method comprises: providing a conductor roll (eg a copper conductor roll) with a conductor wound thereon. In this step, the roll is unwound in preparation.

[0034] In a further step 11 , the method comprises locally coating that portion of the conductor tape which corresponds to the at least one conductor with a local, expandable coating.

[0035] In another step 12, the required conductor is manufactured by separating / separating the conductor from the conductor strip, wherein the conductor can be provided with the correct length. In the case of using a plug-in coil, a so-called hairpin (hairpin-shaped conductor) can also be manufactured in this step by correspondingly bending the straight conductor section.

[0036] In a subsequent step 13 , the method comprises forming a winding of the stator by introducing / arranging conductors into grooves of the stator lamination package.

[0037] In a final step 14 , the method comprises activating the localized, expandable coating on the at least one conductor, so that the coating expands and thereby fixes the conductor within the stator slot.

[0038] Although the manufacturing method according to the present invention Figure 1 The embodiment shown in contains specific manufacturing steps for the conductors for constructing the windings of the stator, but these steps are optional from the perspective of the invention, since appropriately configured conductors from a supplier can be involved, so the manufacturing method can start with providing the stator and introducing the pre-fabricated conductors into the stator grooves. Thus, the method according to the invention can be substantially completed in Figure 1 The process starts at step 13 of the embodiment shown in FIG.

[0039] Figure 2A and Figure 2B Simplified schematic illustrations of a stator 20 made using the method according to the invention are shown, each showing before activation of a localized, expandable coating ( Figure 2A ) and after ( Figure 2B ) is a simplified schematic illustration of a .

[0040] exist Figure 2A In the embodiment of the present invention, partially coated conductors and fully coated conductors are introduced into stator grooves 22 of a stator core 21. Each conductor has a conductor core 23, which can have copper, for example, and an insulating layer 24. In addition, two of the three conductors have a partial (i.e., partial or incomplete) coating 25, while the other conductor is completely covered with the coating 25. The partially coated conductor is distinguished by the presence of uncoated areas 26 on its surface. It should be emphasized that in Figure 2A The configurations shown in the diagram show a very simplified scenario and accordingly only show exemplary scenarios with regard to the number, design and arrangement of partially coated and fully coated conductors. For example, virtually all conductors used can have a partial, expandable coating, wherein the coating pattern on each conductor can be the same or can be different.

[0041] Figure 2AThe expandable coating 25 in the groove 22 is present in its non-activated (ie non-expanded) form. Therefore, the conductor can be introduced into the groove 22 without friction resistance or with little friction resistance. Figure 2B 2 shows the state of the stator 20 after the expandable coating 25 has been activated. Due to the activation, the expandable coating 25 undergoes a volume change, so that the individual conductors are fixed in the grooves 22. In this case, the uncoated areas 26 form flow channels, which provide a connection between the end side and the bottom side of the stator through the grooves 22. Inlets leading into the flow channels on both sides can, however, not necessarily, be explicitly assigned to the flow channels.

[0042] exist Figure 3A and Figure 3B 2 shows two exemplary conductors 30 which can be used to form windings of a stator 20 within the scope of the method according to the invention. Figure 2A and Figure 2B Similarly, each conductor 30 also has a conductor core 23 and an insulating layer 24. Figure 3A The conductor 30 shown in FIG. 1 has a segmented, localized coating 25 in the form of a plurality of discrete layers of coating material. Between the left and right ends of the conductor 30, the fluid can flow along a path formed by the area 26 that is not coated with the expandable material. The areas of the conductor 30 referred to here as ends can be understood as areas that are spaced apart from each other in the longitudinal direction of the conductor 30. This exemplary flow path is Figure 3A This is shown by arrow 31.

[0043] exist Figure 3B 2 shows another example of a structured, localized coating 25 of a conductor 30 with an expandable material. In this example, the localized coating 25 is formed in the form of a line, which forms a spiral-stepped structure 32 around the conductor 30. The region 26 not coated with expandable material correspondingly forms an associated region that is also arranged in a spiral-stepped manner around the conductor 30. This associated region forms a continuous connection between the left end and the right end of the conductor 30 and can therefore be used as a cooling fluid channel.

Claims

1. A method for manufacturing a stator (20) of an electric machine, the method comprising: Providing the stator (20), the stator having at least one stator groove (22), the at least one stator groove being defined by two stator teeth; Introducing conductors (30) into the at least one stator groove (22), each conductor (30) having a conductor core (23) and an insulating layer (24), wherein at least one conductor (30) has an expandable coating (25) applied locally on its surface; The expandable coating (25) is activated to expand the expandable coating (25), thereby fixing the conductors (30) in the stator groove (22), and at least one through-going fluid connection extends through the stator groove (22), the at least one fluid connection being formed by an area (26) of the surface of the at least one conductor (30) not covered by the coating, wherein at least one of the fluid connections or a portion of the fluid connection is formed between at least a pair of adjacent conductors.

2. The method according to claim 1, The expandable coating (25) is activated by heat input.

3. The method according to claim 1, further comprising: providing these conductors (30); The expandable coating (25) is applied to at least one conductor (30), wherein the coating i) either locally applied to the surface of the conductor (30); or ii) Complete application to the surface of the conductor (30) and subsequent local removal.

4. The method according to any one of claims 1 to 3, The expandable coating (25) applied locally on the surface of at least one conductor (30) is structured so that between the regions of the conductor (30) that protrude from the stator after the conductors are inserted into the stator grooves (22), there is at least one continuous path (31) extending on the uncoated surface of the conductor (30).

5. The method according to any one of claims 1 to 3, The partial coating (25) is arranged in the form of a spiral step-like structure (32) on the surface of the at least one conductor (30).

6. The method according to any one of claims 1 to 3, The local coating (25) is arranged in the form of a plurality of mutually separate layers on the surface of the at least one conductor (30), so that between the regions of the conductor (30) which protrude from the stator (20) after the conductors are inserted into the stator grooves, there is a continuous path (31) extending on the uncoated surface of the conductor (30).

7. A stator (20) for an electric machine, the stator having at least one stator groove (22), the at least one stator groove being defined by two stator teeth, wherein the stator (20) further has: Conductors (30) arranged in the at least one stator groove (22), each conductor (30) having a conductor core (23) and an insulating layer (24), wherein the conductors (30) are fixed in the stator groove (22) and the surface of at least one conductor (30) arranged in the stator groove (22) is partially covered by an expandable coating (25); At least one fluid connection extends through the at least one stator groove (22), wherein the fluid connection is formed by an area (26) of the surface of the at least one conductor (30) not covered by the coating, wherein at least one of the fluid connections or a portion of the fluid connection is formed at least between a pair of adjacent conductors.

8. Use of at least one conductor (30) partially coated with an expandable coating (25) to form a winding of a stator (20), wherein each conductor (30) has a conductor core (23) and an insulating layer (24), and wherein the local coating (25) is structured so that uncoated areas (26) of the conductor surface are arranged so that at least one path (31) extends through these areas, the at least one path connecting two areas spaced apart from each other in the longitudinal direction of the conductor (30), wherein at least one of the paths or a part of the path is formed at least between a pair of adjacent conductors.

Images