Method for manufacturing a plug-in coil wire for a stator of an electric rotary machine and method for manufacturing a stator with plug-in coil wires manufactured in this way

Abstract

A method for manufacturing a plug-in coil wire (22) for a stator of an electric rotary machine, wherein the stator comprises: a stator core (12) having a closed stator ring (14) from which stator teeth (16) extend, between which stator slots (24) are formed, and which point towards an air gap arranged at an end radially opposite to the closed stator ring (14), wherein one or more plug-in coil wires (22) are inserted into the stator slots (24), and wherein at least one plug-in coil wire (22) in the axially extending section (28) arranged within the respective stator slot (24) has an axially extending slot (30) by which the plug-in coil wire (22) is divided into two wire parts (32, 34) between which an insulating layer (54) is formed, wherein at the ends (36) projecting axially beyond the stator core (12) of each plug-in coil wire (22) is designed as a solid body (38),wherein the slot (30) of the plug-in coil wires (22) is produced by wire EDM, water jet cutting or laser beam cutting, characterized in that the stator (10) with the plug-in coil wires (22) inserted therein is sprayed with an insulating varnish and dried to form the insulating layer (54) in the slot (30), around the plug-in coil wires (22) and in the stator groove (24) between the stator teeth (16) and the plug-in coil wires (24).

Description

The invention relates to a method for manufacturing a plug-in coil wire and a stator for an electric rotary machine. Such electric rotary machines are used in particular to drive electric vehicles or hybrid vehicles, or can be used as generators in vehicles. These electric rotary machines are typically designed with hairpin or I-wires inserted into the corresponding insulated stator slots. The advantage of this technology is that large conductor cross-sections can be inserted into the slots, allowing high electrical currents to flow through the wires due to low electrical resistance and thus low ohmic losses. Good heat dissipation is also achieved, and only minimal wire insulation is required between the conductors, resulting in high torque density and high continuous torque. The manufacturing of these rotary machines can be highly automated. On the other hand, large conductor cross-sections lead to significant additional losses at high rotational speeds or high electrical frequencies, due to a current displacement effect that is particularly pronounced near the air gap. This effect is reduced by decreasing the conductor cross-section. For this reason, ITBO20090262 A1 proposed dividing a plug-in coil wire into two separate wires with an insulating layer in between, which are then laid opposite each other. Both wires are designed with a 180° twist approximately in the middle, so that one wire points towards the slot opening in its upper region and the other points towards the slot opening in its lower region. While this reduces the current displacement effect, it increases the wiring complexity, as twice the number of wires must be connected. WO 2022 / 029008 A1 relates to a method for the additive manufacturing of a hairpin for an electric motor. US 5,787,567 A relates to a winding conductor material for electrical machines and a method for its production. The task is therefore to develop a method for manufacturing a plug-in coil wire for such a stator, as well as a method for manufacturing such a stator for an electric rotary machine using plug-in coil wires produced in this way. These methods should enable high electric currents with low ohmic resistance and good thermal connectivity, while simultaneously reducing the circuitry and manufacturing effort compared to known solutions. The eddy current effect, or current displacement effect, should also be minimized. This problem is solved by a method for manufacturing a plug-in coil wire for a stator of an electric rotary machine according to claim 1 and a method for manufacturing a stator for an electric rotary machine according to claim 3. The stator of an electric rotary machine comprises a stator core consisting of a closed stator ring and radially extending stator teeth. Stator slots are formed between these teeth, into which one or more plug-in coil wires are inserted. A rotor with permanent magnets is typically arranged within the stator and is rotatable about an axis of rotation. This rotation can be transmitted, for example, via a gearbox to the wheels of a motor vehicle. An air gap is formed between the rotor and the stator. The stator can either have slot openings on the side facing the air gap or be closed. At least one of these plug-in coil wires per stator slot has at least one axially extending section located within the respective stator slot. The slotted plug-in coil wires each have an axially extending slot in this section, i.e., parallel to the axis of rotation of the rotating machine, through which the respective plug-in coil wire is divided into two wire sections. An insulating layer is formed between the two wire sections, electrically isolating them in this area. At the ends projecting axially beyond the stator core, the plug-in coil wires are solid, allowing both wire sections to be connected together.By splitting the wire, losses due to current displacement can be reduced, while the wiring effort is halved compared to fully split wires. Manufacturing costs are also reduced, as both wire segments can be inserted together. According to the inventive method for manufacturing a plug-in coil wire for a stator of an electric rotary machine, the slot of the plug-in coil wire is produced by wire EDM, waterjet cutting, or laser cutting. These methods allow such a plug-in coil wire to be manufactured reliably without damaging the insulation layer, and almost any shape and cross-section can be produced automatically. In particular, the spiral-shaped second section can also be easily produced in this way by simply guiding the cutting tool around the central area. Furthermore, the problem is solved by a method for manufacturing a stator for an electric rotary machine with plug-in coil wires produced in this way, in which at least one of these plug-in coil wires is inserted into each of the stator slots and then the ends of the plug-in coil wires, designed as solid bodies, are connected to a power supply. Accordingly, a simple method for manufacturing, assembling and producing the electrical connection is provided, whereby the rotary machine has a high filling rate, a low current displacement effect and yet high electrical currents with the resulting high achievable power outputs. Regarding the stator for the electric rotary machine, the at least one plug-in coil wire preferably has a first section in which the slot extends axially, a second section in which the slot extends essentially spirally by 180°, and a third section in which the slot again extends axially, thus extending axially from the slot in the first section. This configuration of the plug-in wire reduces eddy current losses and the current displacement effect because the individual cross-sections in the rotary machine are reduced and the wire's position in the slot is altered, so that none of the wires point completely towards the open side of the slot, where the strongest current displacement effect would otherwise occur. Advantageously, the first and third sections have the same axial length, and the second section is formed axially centrally within the stator slot, so that each of the plug-in coil wires points only halfway towards the open side of the slot. This minimizes the resulting current displacement effect. Preferably, in the first section, the first wire segment is directed towards the air gap in which the plug-in coil wire is arranged, while the second wire segment is directed towards the closed stator ring. In the third section, the second wire segment is directed towards the air gap in which the plug-in coil wire is arranged, while the first wire segment is directed towards the closed stator ring. The division thus occurs radially in the groove, alternating the wire segment facing the rotor. This significantly reduces losses at high speeds, allowing the rotary machine to be built smaller or achieving a higher torque density and a higher continuous torque. The plug-in coil wires are advantageously designed as hairpin wires or I-wires, which are easy to insert and connect and are simple to manufacture. It is also preferred to produce the insulating layer using a dried liquid lacquer or a dried liquid resin. This layer can initially be formed only in the slot or can additionally completely surround the wire. The advantage of using these fluids is that very thin insulating layers can be created, so that the fill level in the stator slot remains very high. In an advantageous embodiment, a plug-in coil wire is arranged in each stator slot, the wire segments of which are arranged radially one behind the other in the first and third sections. This allows for particularly large conductor cross-sections. In an alternative embodiment of the invention, two plug-in coil wires are arranged in each stator slot, the four wire parts of which are arranged radially one behind the other in the first section and in the third section, with an insulating layer arranged between each of the four wire parts. Such an arrangement can reduce losses at high speeds by over 40% compared to the solution with one wire per stator slot, thus corresponding to approximately the power loss of a four-layer winding, which, however, requires twice the number of welds for contact. In a further alternative embodiment of the invention, two plug-in coil wires are arranged in each stator slot. One plug-in coil wire, directed towards the air gap, has two wire sections arranged radially one behind the other in the first and third sections, while the other plug-in coil wire, directed towards the stator ring, is formed as a solid body, with an insulating layer arranged between each of the two wire sections and the solid plug-in coil wire. This further reduces manufacturing costs without significantly increasing the current displacement effect. In a further development of the process for manufacturing a plug-in coil wire, the slot is filled with a liquid lacquer to form the insulating layer and then dried. In this case, the liquid lacquer can be applied selectively to the slot, while the remaining insulation can also be formed on the stator teeth. Alternatively, the plug-in coil wire is dipped into a liquid resin to form an outer insulating layer and an insulating layer within the slot, and then dried. This completely eliminates the need for additional insulation surrounding the plug-in coil wires, thus removing any extra process step. Alternatively, the stator, with the inserted coil wires, can be sprayed with an insulating varnish and dried to form the insulating layer in the slot, around the coil wires, and in the stator groove between the stator teeth and the coil wires, thus eliminating one process step. During spraying, the insulating varnish is drawn into the slot and the spaces by capillary action. Alternatively, the stator, with the inserted coil wires, can be immersed in a bath of insulating resin and dried to form the insulating layer in the slot, around the coil wires, and in the stator groove between the stator teeth and the coil wires. During the immersion process, the stator is completely covered with the insulating resin. This also eliminates the need for additional manufacturing steps. Furthermore, it is advantageous if a wire is first unwound from a wire spool and the slots are made, then the wires are cut to length, bent, and insulated. In this way, the slots and insulation can be made directly and fully automatically, thus significantly simplifying the manufacturing process. This document describes the creation of an electric rotary machine, a method for manufacturing plug-in coil wire for such an electric rotary machine, and a method for manufacturing an electric rotary machine using plug-in coil wires produced in this manner. These processes are simple to manufacture and can be carried out with a high degree of automation. Eddy current losses and current displacement effects occurring in the wires are significantly reduced, resulting in low power losses even at high rotational speeds and thus achieving high continuous torques and torque densities. Compared to known designs, electrical contacting is also simplified, as the number of necessary contact points or welds is reduced. An embodiment of a stator according to the invention for an electric rotary machine with the correspondingly manufactured plug-in coil wires is shown in the figures and is described below. Fig. 1 shows a perspective side view of a stator according to the invention with two plug-in coil wires per stator slot. Fig. 2 shows a side view of the stator from Fig. 1. Fig. 2a) shows a section of a sectional view along line IIa-IIa from Fig. 2. Fig. 2b) shows a section of a sectional view along line IIb-IIb from Fig. 2. Fig. 2c) shows a section of a sectional view along line IIc-IIc from Fig. 2. Fig. 3a) shows a perspective view of an I-type plug-in coil wire according to the invention. Fig. 3b) shows the view from Fig. 3a) with the section plane inserted. Fig. 4a) shows a perspective view of a hairpin plug-in coil wire according to the invention. Fig. 4b) shows the representation from Fig.4a) with inserted cutting plane. Fig. 1 shows a stator 10 according to the invention, which has a stator stack 12 which can consist, for example, of stacked lamellar sheets, but can also be manufactured in one piece. This stator assembly 12 has an outer closed stator ring 14, from which stator teeth 16 extend radially inwards. These stator teeth 16 have a tooth root 18, which in the present embodiment is part of the stator ring 14, and extend towards a tooth tip 20. The tooth tip 20 has a widening that prevents plug-in coil wires 22, which are arranged in stator slots 24 formed between the stator teeth 16, from falling radially out of the respective stator slot 24 through slot openings 26 formed between the tooth tips 20. These slot openings can also be omitted, thus allowing this side facing the rotor to be closed as well. An air gap to a rotor (not shown) is located radially inside. In this exemplary stator 10, two plug-in coil wires 22 are arranged radially one behind the other in each stator slot 24, which are either designed as I-wires 22-1 as shown in Fig. 3 or as hairpin wires 22-2 as shown in Fig. 4. These plug-in coil wires 22 are inserted axially into the stator slots 24 and have a slot 30 in their axially extending section 28 arranged within the stator slot, through which each plug-in coil wire 22 is divided into a first wire part 32 and a second wire part 34. At the ends 36 that project axially beyond the stator stack 12 and are bent, the plug-in coil wires 22 are formed as solid bodies 38 without a slot, so that the two wire sections 32, 34 at these ends 36 again form a single, undivided plug-in coil wire 22. Accordingly, these ends 36 can also be electrically contacted, for example, via a welded connection, whereby both wire sections 32, 34 can be contacted together via a single welded connection. Figures 3 and 4 show that the slot 30 has a special shape. In a first axial section 40, the slot 30 extends axially along the length of the plug-in coil wire 22 to approximately the middle of the plug-in coil wire 22, where the slot 30 extends spirally in a second section 42, the spiral extending over an angle of 180°. A third section 44 adjoins this second section 42, in which the slot 30 again extends vertically. The formation of the 180° spiral shape in the second section 42 results in a change in the position of the two wire parts 32, 34 in the stator slot 24. This means that the first wire part 32 in the first section 40 is directed towards the slot opening 26 and thus towards the air gap, while the second wire part 34 in this first section 40 points towards the stator ring 14, while in the third section 44 the second wire part 34 is directed towards the slot opening 26 and thus towards the air gap, while the first wire part 32 is directed towards the closed stator ring 14. By dividing the plug-in coil wires 22 into two parts and changing their position relative to the slot opening 26 and thus to the air gap, the current displacement effect is significantly reduced, which otherwise occurs mainly in the area adjacent to the air gap, but now, on the one hand, cannot extend through the plug-in coil wire 22 due to the change in position and, on the other hand, also occurs to a lesser extent due to the narrower wire parts 32, 34. In the I-wire 22-1 according to Fig. 3, the ends 36 adjoining the slotted area are each formed as solid bodies 38 and bent, which facilitates axial positioning in the stator slot 24. The hairpin wires 22-2 according to Fig. 4 each have two legs 46, 48, wherein the two legs 46, 48 engage in different stator slots 24 and are connected to each other by a deflection SO designed as a solid body 38. Accordingly, at one end 36 of each hairpin wire 22-2, two connection ends 52 are formed, which are also inclined towards the sections of the hairpin wire 22-2 arranged in the stator slots 24. In Figs. 4a) and b), it can also be seen that only one of the two legs 46 is designed with a slot 30, while the other leg 48 forms a plug-in coil wire section 51 designed as a solid body 38. Figures 2a) to c) clearly show that the slotted leg 46 of each hairpin wire 22-2 points towards the slot opening 26 and thus towards the air gap, while the second, unslotted leg 48 is placed in another stator slot 24 adjacent to the stator ring 14 and forms a plug-in coil wire section 51 designed as a solid body 38. While in the cross-section in Figure 2a) both legs 46, 48 are still without a slot and are accordingly designed as solid bodies 38, in the cross-section according to Figure 2b) the leg 46 pointing towards the rotor (not shown) is designed with a vertical slot 30. The two resulting wire sections 32, 34 lie radially one behind the other in the stator slot 24. Radially adjoining them is the second, unslotted leg 48 of the other plug-in coil wire section 51, designed as a solid body 38. The cross-section according to Figure 2b)2c) is located exactly at the center of the axial length of the stator 10, so that the slotted leg 46 facing the air gap is cut centrally in the area of ​​the spiral slot 30 in the second section 42, causing the two wire parts 32, 34 to lie next to each other in the circumferential direction. In the lower region of the stator 10, as shown in Fig. 1 and Fig. 2a), the deflections 50 of the hairpin wires 22-2 are located. The slots 30 are cut into the plug-in coil wire 22 by wire EDM, waterjet cutting or laser beam cutting. This can be done immediately after unwinding the plug-in coil wires 22 from the wire spool and before cutting them to length. It is also important to insulate the two wire sections 32 and 34 from each other and from the stator core 12. For this purpose, an insulating layer 54 can be applied to the slots 30 using an insulating varnish. This layer can also be applied to the outer sections of the plug-in coil wires 22, or the wires can be inserted into insulating bodies that have been previously placed in the stator slots 24. If the insulating varnish is used, it can also be applied by spraying after the plug-in coil wires (22) have been inserted, distributing itself both in the 10 spaces and in the slot 30. Alternatively or additionally, the slotted plug-in coil wires 22 can be immersed in an insulating resin to form the insulating layer 54, so that the insulating resin is deposited both in the slot 30 and on the outside of the plug-in coil wires 22. This can also be done after the slotted plug-in coil wires 22 have been inserted into the stator slots 24, so that the entire stator 10 is immersed in the insulating resin and an insulating layer 20 is formed in the spaces between the plug-in coil wires 22, the stator teeth 16, and the plug-in coil wires 22, as well as in the slot 30. In both cases, the insulating resin or insulating varnish must be allowed to dry to form a reliable insulating layer 54. The plug-in coil wires 22, thus insulated, are inserted axially into the stator slots 24, and their ends 36, which are designed as solid bodies 38, are then electrically contacted. The described stator is easy to manufacture, can be contacted with reduced effort due to the relatively small number of necessary contact points, and yet exhibits low power losses, as eddy current losses and losses due to the current displacement effect are reduced.

Claims

A method for manufacturing a plug-in coil wire (22) for a stator of an electric rotary machine, wherein the stator comprises: a stator core (12) having a closed stator ring (14) from which stator teeth (16) extend, between which stator slots (24) are formed, and which point towards an air gap arranged at an end radially opposite to the closed stator ring (14), wherein one or more plug-in coil wires (22) are inserted into the stator slots (24), and wherein at least one plug-in coil wire (22) in the axially extending section (28) arranged within the respective stator slot (24) has an axially extending slot (30) by which the plug-in coil wire (22) is divided into two wire parts (32, 34) between which an insulating layer (54) is formed, wherein at the ends (36) projecting axially beyond the stator core (12) of each plug-in coil wire (22) is designed as a solid body (38),wherein the slot (30) of the plug-in coil wires (22) is produced by wire EDM, water jet cutting or laser beam cutting, characterized in that the stator (10) with the plug-in coil wires (22) inserted therein is sprayed with an insulating varnish and dried to form the insulating layer (54) in the slot (30), around the plug-in coil wires (22) and in the stator groove (24) between the stator teeth (16) and the plug-in coil wires (24). Method for producing a plug-in coil wire (22) for a stator of an electric rotary machine according to claim 1, characterized in that first a plug-in coil wire (22) is unwound from a wire roll and the slots (30) are made, then the plug-in coil wires (22) are cut to length and bent. Method for manufacturing a stator for an electric rotary machine with plug-in coil wires according to one of claims 1 or 2, characterized in that at least one of the plug-in coil wires (22) is inserted into each stator slot (24) and subsequently the ends (36) of the plug-in coil wires (22), designed as solid bodies (38), are connected to a power supply. Method for manufacturing a stator for an electric rotary machine with plug-in coil wires according to claim 3, characterized in that the at least one plug-in coil wire (22) has a first section (40) in which the slot (30) extends axially, a second section (42) in which the slot (30) extends substantially spirally by 180° and a third section (44) in which the slot (30) again extends axially. Method for manufacturing a stator for an electric rotary machine with plug-in coil wires according to claim 4, characterized in that the first section (40) and the third section (44) have the same axial length and the second section (42) is formed axially centrally within the stator slot (24). Method for manufacturing a stator for an electric rotary machine with plug-in coil wires according to claim 4 or 5, characterized in that in the first section (40) the first wire part (32) is directed towards the air gap in which the plug-in coil wire (22) is arranged, while the second wire part (34) is directed towards the closed stator ring (14), and in the third section (44) the second wire part (34) is directed towards the air gap in which the plug-in coil wire (22) is arranged, while the first wire part (32) is directed towards the closed stator ring (14). Method for manufacturing a stator for an electric rotary machine with plug-in coil wires according to one of claims 3-6, characterized in that the plug-in coil wires (22) are designed as hairpin wires (22-2) or I-wires (22-1). Method for manufacturing a stator for an electric rotary machine with plug-in coil wires according to one of claims 3-7, characterized in that a plug-in coil wire (22) is arranged in each stator slot (24), the wire parts (32, 34) of which are arranged radially one behind the other in the first section (40) and in the third section (44). Method for manufacturing a stator for an electric rotary machine with plug-in coil wires according to one of claims 3 to 7, characterized in that two plug-in coil wires (22) with slots (30) are arranged in each stator slot (24), the four wire parts (32, 34) of which are arranged radially one behind the other in the first section (40) and in the third section (44), wherein an insulating layer (54) is arranged between each of all four wire parts (32, 34). Method for manufacturing a stator for an electric rotary machine with plug-in coil wires according to one of claims 3 to 7, characterized in that two plug-in coil wires (22) are arranged in each stator slot (24), one of which a plug-in coil wire (22) directed towards the air gap has two wire parts (32, 34) arranged radially one behind the other in the first section (40) and in the third section (44), and a plug-in coil wire section (51) directed towards the stator ring (14) is designed as a solid body (38), wherein an insulating layer (54) is arranged between the two wire parts (32, 34) and the plug-in coil wire section (51) designed as a solid body (38).

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