Method for producing a stator with a groove impregnation step using a doctor blade; stator; and tool

Abstract

The invention relates to a method for producing a stator (1) for an electrical machine, wherein in a first step an annular base body (3) provided with a plurality of radially inwardly open slots (2) is provided, in a second step a coil arrangement (4) is at least partially arranged in the base body (3) in such a way that a plurality of coil sections (5) of the coil arrangement (4) are arranged in each slot (2), in a third step a curable filler (6) is introduced into the slots (2) in a liquefied state, filling gaps (7) between the base body (3) and the coil sections (5), which filler (6) cures in a fourth step, wherein the filler (6) is pressed into the slots (2) from a radial inner side (8) of the base body (3) by means of a doctor blade (9) guided along the inner side (8).The invention also relates to a stator (1) and a tool (15) for applying the filler (6).

Description

The invention relates to a method for producing a stator for an electric machine, in particular an electric drive machine of a motor vehicle, such as a car, truck, bus or other commercial vehicle, wherein in a first step an annular base body provided with a plurality of radially inwardly open grooves is provided, in a second step a coil arrangement is arranged at least partially in the base body in such a way that a plurality of coil sections of the coil arrangement are arranged in each groove, in a third step a curable filler is introduced into the grooves in the liquefied state, filling gaps between the base body and the coil sections, which filler finally cures / is cured in a fourth step. Furthermore, the invention relates to a stator, preferably produced by such a method; furthermore, the invention relates to a tool for applying a filler in this method.It is generally known to fill those cracks / cavities / gaps within the grooves between the corresponding coil sections and the base body / the side walls of the base body with filler, which usually has a resin base and is thus also alternatively referred to as filling resin. It is also known to use the so-called dripping method for this purpose, in which the liquid resin is dripped on from an axial end face of the assembly of base body and coil arrangement, for example on the side of a winding head, which is finally sucked into the respective groove axially by the force of gravity and the capillary force.In this regard, it has been found that the known drop methods are relatively complicated to implement, however. Also, the resin takes a relatively long time until it fills the groove throughout its length. Furthermore, there is the disadvantage that excess filler residues present have to be removed on the side of the axial end faces in a relatively complicated manner.It is therefore an object of the present invention to provide a method and a stator which can be manufactured as quickly as possible but at the same time permits operation of the electric machine as efficiently as possible.This is achieved according to the invention in that the filler is pressed into the grooves from a radial inner side of the base body by means of a doctor blade guided along the inner side.This not only accelerates the production process, but also significantly homogenized the filling degree of the filler within the grooves. Residues remaining outside the grooves are avoided. The result is improved efficiency.Further advantageous embodiments are claimed with the dependent claims and are explained in more detail below.Accordingly, it is furthermore advantageous if the base body is rotated about its central axis in the third step. For filling all the grooves, it is furthermore advantageous if the stator is even rotated by several full revolutions (i.e. several times by 360°). The stator 1 ( / its central axis) is preferably aligned horizontally. A tool serving for applying the filler can thus be designed as simply as possible.For the production process, it is furthermore advantageous if the filler is applied to the inner side of the base body in the third step, in a lower half, preferably a lower third, of the base body. Further preferably, the filler is applied in the region of a deepest point of the inner side of the base body. As a result, the filler can be pre-dispersed, already before being pressed in by the doctor blade, before the stripping edge of the doctor blade by the acting force of gravity.In this regard, it is also advantageous if the filler is applied in the third step by means of a lance projecting axially into the base body. The filler is thereby distributed using the simplest possible means. It is thus likewise expedient if the filler is applied at an axial center of the stator / base body.It is furthermore advantageous if the filler is applied in the third step and subsequently cures in the fourth step in such a way that the main body is covered on its inner side with a protective layer (consisting of this filler), wherein the protective layer preferably runs around the entire circumference and continuously. This results in a skillful sealing of the base body with respect to the environment.In order to achieve a further improved efficiency, it is advantageous if the protective layer has a thickness of between 0.01 mm and 0.1 mm.With regard to the application of the filler, it has proven to be particularly efficient if the doctor blade is pressed against the base body in the third step with a pressure of 2 to 3 N per 1 cm length of the doctor blade.The invention further relates to a stator for an electric machine, having an annular base body provided with a plurality of radially inwardly open grooves and a coil arrangement arranged at least partially in the base body, wherein a plurality of coil sections of the coil arrangement are arranged in each groove of the base body, and wherein a filler is filled in gaps present within the grooves between the base body and the coil sections, which filler at least partially directly forms an inner side of the stator and directly covers at least one radially innermost coil section (preferably without the interposition of an insulating paper or any attachment, such as a groove wedge, radially outwards).With respect to the stator, it is further advantageous if the filler comprises an additive / additive particle of a weight proportion of between 5 and 80 wt %, more preferably between 20 and 60%, (with respect to the total weight of the filler introduced). Additive particles may be, for example, aluminum oxide particles or boron nitride particles, which are preferably homogeneously distributed in a resin base of the filler.Furthermore, the invention relates to a tool for applying a filler in a method according to the invention according to at least one of the embodiments described above, having an elongated doctor blade and a lance arranged offset to the doctor blade, wherein a discharge opening of the lance is arranged centrally with respect to the doctor blade.In order to make possible the most efficient possible production and functioning of an electric machine, it is furthermore advantageous if the squeegee is provided with a contour on its longitudinal edge prepared for painting on the inner side of the base body, which contour ensures that the protective layer is also correspondingly contoured in opposite directions on an inner side of the stator / base body.In order to further optimize filling, it is advantageous if the doctor blade is heated, i.e. preferably equipped by means of its own heating device or subjected to heat by a separate heating device.The invention is now explained in more detail below with reference to figures.The following are shown: FIG. 1 shows a front view of a stator produced according to the invention according to a preferred exemplary embodiment, wherein the method step in which a liquid filler provided for filling the slots of the stator is applied to a radial inner side of a base body of the stator is illustrated, and FIG. 2 shows a perspective illustration of the stator according to FIG. 1.The figures are merely schematic in nature and serve exclusively for understanding the invention. The same elements are provided with the same reference numerals.FIGS. 1 and 2 clearly show a stator 1 produced according to the invention with regard to its basic structure. The stator 1 is designed as a stator 1 of an electric machine, which preferably serves as a drive machine of a motor vehicle. The stator 1 is formed annularly as a whole and is accommodated fixedly in the housing in an operating state of the electric machine. A rotor of the electric machine is then rotatably mounted radially inside the stator 1 in the usual manner. An axis of rotation of the rotor corresponds to a longitudinal axis / central axis 10 of the stator 1.The stator 1 has a base body 3, which is again annular and is typically formed from a laminated core and thus has a multiplicity of individual laminations which are stacked one on top of the other in the axial direction (that is to say along the central axis 10).A coil arrangement 4 is accommodated / arranged in the base body 3. This coil arrangement 4 is formed by what is known as hair-pin technology and accordingly has a plurality of segments which are individually inserted axially into the grooves 2 and are connected to one another. Alternatively, however, the coil arrangement 4 is also formed in another manner, for example by means of a winding technology and thus as a usual coil winding. The regions of the coil arrangement 4 which project axially out of the base body 3 are referred to as end windings 14. Axially between the end windings 14, i.e. in the region in which the coil arrangement 4 is arranged within the base body 3, the coil arrangement 4 has a plurality of coil sections 5 running parallel to one another.The base body 3 is equipped with a plurality of slots / stator slots 2 arranged distributed in the circumferential direction. Each groove 2 penetrates the main body 3 completely in the axial direction and is open to a radial inner side 8 of the stator 1 / of the main body 3. The term radial / radial direction is to be understood as meaning a direction perpendicular to the central axis 10. A plurality of coil sections 5 of the coil arrangement 4 are arranged in each slot 2. The coil sections 5 do not project inwardly from the groove 2 in the radial direction, but are arranged completely radially within this groove 2.Between the individual coil sections 5 of the coil arrangement 4 and the base body 3 / the side flanks formed by the base body 3 and delimiting the groove 2, there are (axial and radial) gaps 7 which, in the finished state of the stator 1, are filled with a filler 6 (in the axial direction / along the entire length of the grooves 2 as well as in the radial direction / over the entire height of the grooves 2). Optionally, the slots 2 in the finished state of the stator 1 are additionally closed with slot wedges which prevent the coil sections 5 from slipping in the radial direction. Also, more preferably, in the finished state of the stator 1, insulation paper is wound around the coil portions 5 arranged within a groove 2.The filler 6 per se is introduced over the entire radial height of each groove 2 and thus at least partially directly forms a radial inner side 8 of the stator 1 and of the base body 3 in the finished state of the stator 1. The filler 6 is also introduced over the entire axial length of each groove 2. The filler 6 thus directly fills the gaps 7 completely.The manufacturing method of the stator 1 implemented in this regard according to the invention will be described in detail below.The filler 6 is made of a resin material / a resin base. The filler 6 is liquefied during the production of the stator 1 and conveyed into the respective groove 2. After curing of the filler 6, the filler 6 then forms a direct constituent of the stator 1.The filler 6 preferably has additive particles dispersed in the resin material, such as alumina particles or boron nitride particles. The proportion by weight thereof is preferably between 50 and 80% by weight of the total filler 6.Furthermore, it should be pointed out that the filler 6 is preferably introduced into the base body 3 in such a way that, in the fully cured state and thus in the fully produced state of the stator 1, it forms a continuously encircling protective layer 12 over the entire inner side 8 of the stator 1 / of the base body 3. The protective layer 12 may have a thickness (radial dimension) between 0.01 mm and 0.1 mm.In order to carry out the production method according to the invention for this rotor, it should be pointed out that, first of all, in a first step, the ring-shaped base body 3 provided with the radially inwardly open grooves 2 is provided. Subsequently, in a second step, the coil arrangement 4 is arranged in the base body 3, wherein a plurality of coil sections 5 of the coil arrangement 4 are present in each groove 2. Finally, in a third step, the curable filler 6 is introduced into the grooves 2 in the liquefied state, with complete filling of the gaps 7.As shown in FIGS. 1 and 2 by the arrow running in the shape of a curve, the stator 1 / the assembly of the base body 3 and the coil arrangement 4 is rotated about the central axis 10 of the stator 1 during the third step. It can also be seen in FIGS. 1 and 2 that in this third step the liquid filler 6 is distributed on the radial inner side 8 of the base body 3 by means of a doctor blade 9 and is pressed directly into the grooves 2. The doctor blade 9 is guided along this inner side 8 while bearing against the radial inner side 8. In this case, the filler material which escapes in the axial direction centrally from a lance 11 in the region of its discharge opening 13 is distributed by means of the doctor blade 9 and at the same time pressed into the grooves 2 with a certain force (by action of a certain force on the doctor blade 9. A pressure force of 2 to 3 N per 1 cm length of the doctor blade 9 on the base body 3 is advantageous.The squeegee 9 and the lance 11 together form a tool 15. The tool 15 is arranged substantially centrally on the base body 3 during the application of the filler 6 (in particular with respect to the squeegee 9 and the application opening 13 of the lance 11).The doctor blade 9 preferably has a contour on its longitudinal edge 16 guided along / abutting the inner side 8. This serves to provide the applied filler 6 on the inner side 8 with a surface structure / contour that is formed negatively thereto. This is used in particular to reduce drag torques which occur during operation of the engine. It is furthermore advantageous if the doctor blade 9 is heated by means of a heating device which is not shown in any more detail here for the sake of clarity.It is advantageous if the doctor blade 9 is moved around the inner side 8 over at least one revolution, more preferably over several revolutions (through 360° in each case) in the third step.The tool 15, as can also be seen easily in FIG. 1, is positioned in a lower half of the stator 1 during the application of the filler and thus serves to apply the filler 6 to the inner side 8 on a lower side (viewed in the acting gravitational field), that is to say at least one lower half, more preferably a lower third.In other words, the embodiment according to the invention results in faster and shorter impregnation paths, since the impregnating resin (filler 6) is applied directly into the groove 2 from the radius interior. The horizontal stator position provides symmetrical flow paths from (axially) inward to outward. In addition, a more direct filling of the groove base is possible.In the manufacturing process, the wires (coil portions 5) are temporarily held in position until the impregnating resin has cured and the wires are permanently fixed. As a result, a groove wedge can even be dispensed with. By eliminating the groove wedge, the wires can slip closer to the inside of the radius until they are permanently fixed (gelling and curing of the impregnating resin).Impregnating resins with a higher filler content, which in principle have less suitable flow properties than impregnating resins without or with a low filler content, can therefore now penetrate into shorter flow paths and be used. Doctoring the impregnating resin directly from the inside of the radius significantly shortens the paths.An adhesive surface of the impregnating resin is enlarged by the omission of the slot wedge, and the surface scraping on the inner lateral surface (inner side 8) of the stator 1 enables the fixing of additional functional parts.In the production process, a rotating gripper preferably holds the temperature-controlled stator 1 on its outer lateral surface. As a result, the lance 11 and the additional doctor blade 9 can be positioned centrally in the inner stator region. The resin is applied from the lance 11 in the central plane of the stator 1, and a squeegee 9 pushes the resin into the slots 2 while the stator 1 rotates. The resin flows directly into the groove depth (in the radial direction) and can also distribute symmetrically from the inside to the outside (in the axial direction) uniformly, since the stator 1 rotates in the horizontal position.List of reference characters1 Stator 2 Slot 3 Base body 4 Coil arrangement 5 Coil section 6 Filler 7 Gap 8 Inner side 9 Doctor blade 10 Central axis 11 Lance 12 Protective layer 13 Application opening 14 Winding head 15 Tool 16 Longitudinal axis

Claims

Method for producing a stator (1) for an electric machine, wherein in a first step an annular base body (3) provided with a plurality of radially inwardly open grooves (2) is provided, in a second step a coil arrangement (4) is arranged at least partially in the base body (3) in such a way that a plurality of coil sections (5) of the coil arrangement (4) are arranged in each groove (2), in a third step a curable filler (6) is introduced into the grooves (2) in the liquefied state, filling gaps (7) between the base body (3) and the coil sections (5), which filler (6) cures in a fourth step, characterized in that the filler (6) is pressed into the grooves (2) from a radial inner side (8) of the base body (3) by means of a doctor blade (9) guided along the inner side (8).Method according to claim 1, characterised in that the base body (3) is rotated about its central axis (10) in the third step.Method (1) according to claim 1 or 2, characterised in that the filler (6) is applied to the inner side (8) of the base body (3) in the third step, in a lower half of the base body (3).Method (1) according to one of Claims 1 to 3, characterized in that, in the third step, the filler (6) is applied by means of a lance (11) which projects axially into the main body (3).Method (1) according to one of Claims 1 to 4, characterized in that the filler (6) is applied in the third step and subsequently cures in the fourth step in such a way that the main body (3) is covered on its inner side (8) with a protective layer (12).Method (1) according to claim 5, characterised in that the protective layer (12) has a thickness between 0.01 mm and 0.1 mm.Method (1) according to one of Claims 1 to 6, characterized in that, in the third step, the doctor blade (9) is pressed against the base body (3) with a pressure of 2 to 3 N per 1 cm length of the doctor blade (9).Stator (1) for an electric machine, having an annular base body (3) provided with a plurality of radially inwardly open slots (2) and a coil arrangement (4) arranged at least partially in the base body (3), wherein a plurality of coil sections (5) of the coil arrangement (4) are arranged in each slot (2) of the base body (3), and wherein a filler (6) is filled in gaps (7) between the base body (3) and the coil sections (5) present within the slots (7), said filler (6) at least partially directly forming an inner side (8) of the stator (1) and directly covering at least one radially innermost coil section (5).Stator according to Claim 8, characterized in that the filler (6) has additive particles of a proportion by weight of between 5 and 80% by weight.Tool (15) for applying a filler (6) in a method according to one of Claims 1 to 7, having a doctor blade (9) of elongate design and a lance (11) arranged offset with respect to the doctor blade (9), wherein an application opening (13) of the lance (11) is arranged centrally with respect to the doctor blade (9).

Images