CN107852056B

CN107852056B - Stator with insulated bar winding for an electrical machine

Info

Publication number: CN107852056B
Application number: CN201680046150.3A
Authority: CN
Inventors: B·冯·毛奇; N·皮塔维斯; A·瓦西列夫
Original assignee: Continental Automotive GmbH
Current assignee: Vitesco Technologies GmbH
Priority date: 2015-09-03
Filing date: 2016-07-27
Publication date: 2020-10-09
Anticipated expiration: 2036-07-27
Also published as: WO2017036687A1; DE102015216840A1; EP3345284A1; CN107852056A

Abstract

The invention relates to a stator (1) for an electric machine (34), having a laminated core (2) which has grooves (4) extending in an axial direction (3) of the stator (1) and which has conductor bars (21) which form an electrical winding of the stator (1), in each case at least one of the conductor bars being arranged in one of the grooves (4), wherein each bar (21) is electrically insulated from the laminated core by a respective electrical insulation element (22). The stator (1) can be manufactured efficiently. The present invention provides: the respective electrically insulating element (22) is configured as a hose element (23) formed of thermoplastic and surrounding the bar (21).

Description

Stator with insulated bar winding for an electrical machine

Technical Field

The invention relates to a stator for an electric machine, an electric machine having a stator according to the invention, a motor vehicle, and a method for manufacturing a stator. The stator has a laminated core with recesses, in each of which at least one conductor bar (bar) is arranged, wherein all the bars form the electrical winding of the stator. Each bar is insulated from the laminated core by means of an electrical insulating element.

Background

In the case of a particular type of stator, it is provided in the prior art to coat each conductor bar with an electrically insulating surface coating agent. Subsequently, the bars are mounted in the grooves in the laminated core and fixed using insulating paper. Finally, the insulating paper is impregnated with a casting compound, in particular an impregnating resin. As a result, the bars are fixed in the grooves and insulated from the laminated core.

The manufacturing process known from the prior art is time consuming, since a high precision is required for arranging the bars together with the insulating paper. Furthermore, impregnation of the insulating paper and subsequent curing of the cast compound takes several hours.

Disclosure of Invention

The invention is based on the following objectives: an electric machine, in particular for a motor vehicle, which can be produced efficiently is obtained.

The invention provides a stator for an electric machine. In a manner known per se, the stator has a laminated core with grooves which extend in the axial direction of the stator. The axial direction is oriented together with the intended axis of rotation of the rotor to be arranged in the stator. The stator also has electrically conductive bars constituting the electrical windings of the stator, in each case at least one of the electrically conductive bars being arranged in one of the grooves. In other words, the stator has bar windings. In each case, two bars are preferably arranged in each groove and the bars are connected to one another to form a double-layer winding. Each bar is electrically insulated from the laminated core by a respective electrical insulation element.

In contrast to the prior art, however, the electrically insulating element is not subsequently formed from a layer of surface coating agent and insulating paper impregnated with the casting compound. In contrast, for efficient manufacturing of the stator, it is provided that the respective electrically insulating element of each bar is configured as a hose element formed of thermoplastic and surrounding the respective bar. In other words, each bar is encased or encased by plastic along its length. In other words, each bar has a jacket formed of plastic.

The present invention provides the following advantages: each bar may be manufactured or obtained separately together with its electrically insulating elements. Each bar can then be inserted in the recess together with its electrically insulating element in finished form. Subsequently, no further processing steps are required to insulate the bars from the laminated core.

The invention also includes alternative developments, the features of which provide additional advantages.

According to one development, the plastic of the respective hose element is arranged around the respective bar by means of extrusion. In other words, the plastic is arranged or cast around the bar in a soft or fluid state by means of extrusion. This provides the following advantages: the bars may be provided with their respective electrically insulating elements one after the other by the machine in a continuous or ongoing extrusion process. This makes the manufacture even more efficient.

According to one development, the groove width of the respective groove in which the hose element is arranged is at most 0.2mm, in particular 0mm, larger than the outer diameter of the hose element itself. In other words, in the circumferential direction of the stator, in each groove the bar together with its hose element has a resulting play or free space of at most 0.2mm, in particular at most 0 mm. This provides the following advantages: each bar can be fixed or attached in the groove with little expenditure. It is sufficient to fold or flex the end of the bar protruding from the laminated core, for example, so that the bar sits securely in the groove together with its hose element.

One development here provides that the bar bends plastically and/or elastically in the groove and thus has mechanical stresses which press the hose element against the groove wall of the groove. This provides the following advantages: heat conduction between the laminated core and the bars is ensured or guaranteed. Such folding can be achieved, for example, by means of the described folding or folding of the bar ends projecting from the laminated core.

According to one development, the wall thickness of the hose element of each bar is in the range 0.1mm to 0.5 mm. For example, the wall thickness may be 0.3 mm. In other words, in each direction, there is a plastic layer between the bars and the laminated core, said plastic layer having a thickness or wall thickness in the range of 0.1mm to 0.5 mm. This provides the following advantages: each bar is reliably electrically insulated from the laminated core by means of the hose element only. Furthermore, a reliable heat conduction with a specific size is provided.

According to one development, the recess is free of casting compound. In other words, with the stator it is possible to dispense with pouring out the casting compound, for example the impregnating resin. Thus, this time consuming manufacturing step is avoided.

According to one development, the plastic has or is formed from a polyamide and/or polyphenylene sulfone (PPSU) and/or polyphthalamide (PPA). These plastics have proven to be particularly advantageous when using a stator manufactured in the described manner.

As for the bars themselves, one development provides that each bar is formed of copper. This results in a suitable conductivity of the winding. Furthermore, the deformability of the bars is additionally ensured, so that the plastic of the hose element is pressed against the groove wall by flexing each bar.

The invention also comprises an electric machine with an embodiment of the stator according to the invention. The rotor of the motor is rotatably mounted in the stator. The electrical machine can be produced with a particularly small number of working steps, since in the described manner the stator can be produced by means of the simultaneous insertion of the bars together with their insulating elements into the laminated core and the subsequent bending of the bar ends.

Particularly preferably, provision is made for the electric machine to be configured as a starter generator of the motor vehicle or as an electric motor of a brake assistance system of the motor vehicle. In both applications, it is evident that a stator manufactured in the manner of the invention has sufficient heat transfer between the bars and the laminated core, with the result that the absence of casting compound in particular does not constitute a disadvantage.

Finally, the invention also comprises a motor vehicle in which an electric machine is obtained or arranged in the manner described.

To manufacture embodiments of the stator according to the invention, the invention also results in a method for manufacturing embodiments of the stator according to the invention. In the method according to the invention, a laminated core is obtained with grooves which extend in the axial direction of the stator in a known manner. For each recess, at least one conductor bar is obtained. As previously mentioned, two bars are preferably provided per recess. In order to be able to subsequently arrange the bars in the recesses and in the process to obtain an electrical insulation between each bar and the laminated core with a few working steps, it is provided according to the invention to enclose each bar obtained with a hose element which is formed from a thermoplastic material and which constitutes the electrical insulation element already described. Each bar is inserted into a correspondingly provided recess together with the hose element which accordingly surrounds it. In other words, after each bar is inserted into the respective groove, the electrical insulation of the bar with respect to the laminated core is also ensured at the same time. Therefore, no additional work step is required to ensure electrical insulation after insertion of each bar.

In order to obtain said bars with corresponding hose elements, a development provides for obtaining, for the purpose of obtaining bars, wires with plastic arranged around them by means of extrusion. Separating the wires and plastic into bar and hose elements. In other words, it is possible to obtain, for example, a roll with wires already encased in plastic. Each bar can be obtained in an automated manner by unwinding the wire from a roll and cutting or separating the wire into individual bars. In this context, the plastic may be arranged continuously along the wire. In order to subsequently obtain the hose element, it may be provided that the insulation, that is to say the plastic, is removed from the end of the bar.

The wire may be, for example, a round wire or a ribbon conductor.

Since the bars are already obtained together with their hose elements before being inserted into the respective grooves, according to one embodiment, each bar can advantageously be inserted into one of the grooves together with its respective hose element in each case. The hose element is in particular adhered to the bar here, with the result that an adjustment of each hose element in the groove is not necessary or can be dispensed with.

One development provides that each bar inserted into one of the grooves is shaped by flexing and thus its respective hose element is pressed against the groove wall of the respective groove. This creates a contact point between the hose element and the groove. This ensures in particular that there is a heat transfer path between the laminated core and the bars which is free of air.

Drawings

Exemplary embodiments of the invention are described below, in which:

figure 1 shows a schematic representation of a perspective view of an embodiment of a stator according to the invention,

fig. 2 shows a schematic representation of the stator of fig. 1, wherein only a single electrical coil is shown,

figure 3 shows a schematic representation of a cross section of a stator,

figure 4 shows a schematic representation of a perspective view of a single conductor element of the stator,

figure 5 shows a schematic representation of a side view of a conductor element,

FIG. 6 shows a schematic representation of a cross section of a conductor element, and

fig. 7 shows a schematic representation of an embodiment of the motor vehicle according to the invention.

Detailed Description

The exemplary embodiments explained below are preferred embodiments of the present invention. The described components of the embodiments each represent a separate feature of the invention, which features are to be considered independently of one another and each also independently of one another for the development of the invention, and can therefore also be considered as components of the invention, individually or in combinations other than those shown. Furthermore, other features of the invention already described may also be added to the described embodiments.

In the figures, elements having the same function are provided with the same reference symbols, respectively.

Fig. 1 shows a stator 1 for an electric machine. The stator 1 may be provided for a starter generator of a motor vehicle, for example. The stator 1 has a laminated core 2 which can be formed in a manner known per se from soft-magnetic metal sheet layers (coercive field strength below 1000A/m) which are electrically insulated from one another and are stacked or layered in the axial direction 3.

In the recesses 4 of the laminated core 2, in each case two

conductor elements

6, 7 have been inserted through the axial recess openings 5. For the sake of clarity, only some specific elements have been provided with reference signs in each case. The

conductor elements

6, 7 of each groove 4 are arranged aligned in the radial direction 8, one behind the other. In each case, the radial direction 8 is directed perpendicularly outwards from an axis 9 by which the axial direction 3 is defined. The axis 9 corresponds to the intended axis of rotation of the rotor which may be arranged in the stator.

The different radial distances between the

conductor elements

6, 7 result in two rings or layers 10, 11, wherein the radially outer conductor element 6 forms the layer 10 and the radially inner conductor element 7 forms the layer 11. The

layers

10, 11 are part of a double layer winding 12 of the stator 1. In the example shown, the double-layer winding 12 comprises six electrical coils, each electrical coil being produced by connecting a respective subset of the

conductor elements

6, 7. In each case, one conductor element of the outer layer 10 and one conductor element of the inner layer 11 form a phase connection or coil connection 13 of one of the coils. The coil connections 13 of the coils are each arranged in a connection region 14.

For illustration purposes, fig. 2 shows a single electrical coil 15. The illustration in fig. 2 corresponds to the illustration in fig. 1, wherein all those

conductor elements

6, 7 associated with the other electrical coils are omitted. The coil 15 shown in fig. 2 has a total of three turns or turns 16, which are electrically connected to one another within the connection region 14 by turn connections 17.

To form the turns 16 of the coil 15, the conductor element 6 of the outer layer 11 has been inclined or bent in the circumferential direction U1, while the conductor element 7 of the inner layer 11 has been bent in the opposite circumferential direction U2. The

conductor elements

6, 7 of the two

layers

10, 11 are thus interlocked, with the result that the tilting zone has a tilting angle with respect to the end face 18. The conductor end also has a conductor end oriented parallel to the axis 9. For this purpose, the conductor ends have an offset.

The tilt angles of all the tilted regions of the conductor end portions are the same. These conductor ends are thus particularly close one on top of the other. The conductor end is part of the winding head 20 on the end face 18 of the laminated core 2.

Fig. 3 shows how the

electrical conductor elements

6, 7 in the interior of the laminated core are electrically insulated from the soft-magnetic sheet metal layer of the laminated core 2. For the sake of clarity, in each case only a few reference symbols have been given to the designated elements in fig. 3. Each

conductor element

6, 7 is formed by a conductor bar 21 and an electrically insulating element 22.

Fig. 4 again shows a single

electrical conductor element

6, 7 with a conductive bar 21 and an electrically insulating element 22 alone. In each case, the bars 21 may be strip conductors or flat wires. The material of the bar 21 may be, for example, copper. The electrically insulating element 22 is configured as a sheath or hose element 23.

Fig. 3 shows how each bar 21 is electrically insulated from the laminated core 2 by the material of the hose element 23 by means of an insulating element 22. The hose element 23 is formed from a thermoplastic which may have, for example, polyamide and/or PPSU and/or PPA.

Fig. 3 also shows how each bar 21 presses against the groove wall 24 of the respective groove 4 in the region of each winding head 20 as a result of the interlocking or flexing shown in fig. 1, wherein the bars 21 are mechanically supported or flexed.

The plastic of the hose element 23 can already be applied to the wire rod 21 by means of extrusion.

For this purpose, each bar 21 or the wires from which the bars 21 are manufactured by separating them are led through an extrusion arrangement (not shown). In which an annular gap is located from which the plastic emerges in a deformable or liquid or fluid state. As a result, a hose is produced which rests on the bar 21 or the wire.

Fig. 5 shows how, in the manufacture of a bar 21 from a wire, this wire is divided into bars 21 having a bar length 25. Here, there may be provided: the end portions 26 are formed by removing the plastic insulation of the hose elements 23 from the bars 21, with the result that each hose element 23 has an insulation length 27 which is less than the bar length 25. The bar length may be, for example, in the range of 8cm to 15 cm.

Fig. 6 shows how the bar 21 is enclosed with plastic by means of a hose element 23, wherein the hose element 23 has a layer thickness or wall thickness 28 which can be in the range from 0.1mm to 0.5 mm. The edge 29 of the bar 26 preferably has a curved portion or radius of curvature 30 in the range of 0.5mm to 1.5 mm. This results in the following advantages: the edge 29 does not cut or tear the hose element 23 during the vibrating movement.

The outer diameter 32 of the conductor elements 6, 7 (that is to say the outer diameter 32 of the hose element 23 in the circumferential direction U1, U2) is at most 0.2mm smaller than the groove width 33 in this direction. The hose element 23 is preferably in contact with two groove walls opposite to each other.

Fig. 7 shows how the motor 34 can be obtained by means of the stator 1. In the case of the motor 34, a rotor 35 is rotatably mounted in the stator 1. The rotor 35 is connected to the shaft 36 in a rotationally fixed manner. The motor 34 may be mounted in a motor vehicle 37, for example. The motor vehicle 37 may be, for example, an automobile, specifically, a passenger car or a truck. The shaft 36 may be coupled to a vehicle component 38, which may be, for example, an internal combustion engine or a pump for a hydraulic brake circuit of a brake assist system. The electric motor 34 can be driven in a manner known per se by alternately energizing the electric coils of the stator 1 by means of an inverter. This generates a rotating magnetic field inside the stator, which drives the rotor 35. The rotor 35 then rotates about the axis 9.

In general, the examples show how the electrical insulation of the copper wire rods of a stator can be obtained by plastic coating applied by extrusion. The thickness of the plastic layer can be selectively set in such a way that an extruded pin or an extruded bar can be inserted directly into the groove 4 in the laminated core 2 and subsequently interlocked or bent or twisted. An advantage over the prior art is that the costly process of groove insulation can be eliminated. Specifically, it is not necessary to place the insulating paper in the grooves and then impregnate the insulating paper with the impregnating resin. Another advantage is that neither the insulating paper nor the insulating surface coating on the wire rod is damaged.

The hose element made of thermoplastic is flexible and adapts to the shape of the bar during flexing or twisting. A hose element made of plastic also has sufficient mechanical load-bearing capacity and, nevertheless, a sufficiently thin plastic coating can be selected.

Thus, there is an overall savings in manufacturing steps or processing steps and an associated cost reduction. Furthermore, the stator 1 can be manufactured with a relatively short period of time. The plastic coating applied by extrusion has an improved mechanical load-bearing capacity compared to the surface coating of the bar 21 which has an electrically insulating surface coating and subsequently fixes the bar in the groove 4 by means of insulating paper and casting compound.

The examples thus generally show how the invention permits the use of a thermoplastic jacket for a ribbon conductor for the manufacture of motor windings.

Claims

1. A stator (1) for an electrical machine (34) having a laminated core (2) with grooves (4) extending in an axial direction (3) of the stator (1), and having conductor bars (21) constituting electrical windings of the stator (1), at least one of which is arranged in one of the grooves (4), wherein each conductor bar (21) is electrically insulated from the laminated core by a respective electrically insulating element (22), characterized in that the respective electrically insulating element (22) is configured as a hose element (23) formed from a thermoplastic and surrounding the conductor bar (21), wherein the conductor bar (21) is plastically and/or elastically flexed in the groove (4) and thus has mechanical stress, the mechanical stress presses the hose element (23) against a groove wall (24) of the groove (4), the conductor bar (21) flexing in the circumferential direction.

2. A stator (1) according to claim 1, wherein the plastic of the respective hose element (23) is arranged around the respective conductor bar (21) by means of extrusion.

3. Stator (1) according to any of the preceding claims, wherein the respective groove width (33) of the grooves (4) in which the hose element (23) is arranged is at most 0.2mm larger than the outer diameter (32) of the hose element (23).

4. Stator (1) according to claim 1 or 2, wherein the hose element (23) has a wall thickness (28) in the range of 0.1mm to 0.5 mm.

5. Stator (1) according to claim 1 or 2, wherein the grooves (4) are free of cast compound.

6. Stator (1) according to claim 1 or 2, wherein the plastic has polyamide and/or polyphenylene sulfone and/or polyphthalamide.

7. A stator (1) according to claim 1 or 2, wherein each conductor bar (21) is formed of copper.

8. An electrical machine (34) having a stator (1) according to any of the preceding claims, wherein a rotor (35) is rotatably mounted in the stator (1).

9. The electric machine (34) of claim 8, wherein the electric machine (34) is configured as a starter generator or as an electric motor for a brake assist system of a motor vehicle (37).

10. A motor vehicle (37) having an electric machine (34) according to claim 8 or 9.

11. A method for manufacturing a stator (1) according to any one of claims 1 to 7, wherein in the method a laminated core (2) with grooves (4) is obtained, which grooves extend in the axial direction (3) of the stator (1), and at least one conductor bar (21) is obtained for each groove (4), characterized in that each conductor bar (21) obtained is enclosed by a hose element (23) formed of thermoplastic, and that each conductor bar (21) is inserted into the respectively provided groove (4) together with the hose element (23) respectively enclosing it, wherein the conductor bar (21) is plastically and/or elastically flexed in the groove (4) and thus has a mechanical stress which presses the hose element (23) against a groove wall (24) of the groove (4), the conductor bar (21) is bent in the circumferential direction.

12. Method according to claim 11, wherein, in order to obtain the conductor bar (21), a wire is obtained around which plastic is arranged by means of extrusion, and the wire is divided into the conductor bar (21) and the plastic into the hose element (23).

13. A method according to claim 11 or 12, wherein each conductor bar (21) is inserted into one of the grooves (4) together with its respective hose element (23) in each case.

14. Method according to any one of claims 11 to 12, wherein each conductor bar (21) inserted into one of the grooves (4) is shaped by flexing and thus the respective hose element (23) of the conductor bar (21) is pressed against a groove wall (24) of the respective groove (4).