Stator for electric motor

Abstract

To provide a stator for an electric motor with favorable characteristics in terms of manufacturing and operation.SOLUTION: A stator yoke (12) and a star-shaped stator (14) are each formed by a laminated core, and the laminated core of the star-shaped stator (14) includes a metal sheet layer (26) consisting of a circumferentially closed stator metal sheet (28) with stator teeth (32) interconnected via a pole shoe web (30), and a metal sheet layer consisting of individual stator teeth (32) separated from each other in the circumferential direction. Each pole shoe web (30) has at least one material recess (16) extending radially.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a stator for an electric motor according to the preamble of claim 1.

[0002] From DE 10 2016205538 A1, a stator for an electric motor is already known which has a hollow cylindrical stator yoke and a star stator arranged in the stator yoke, the star stator having radially outwardly directed stator teeth whose tips, in the assembled state, rest against corresponding connecting points on the inner circumferential surface of the stator yoke.

[0003] The object of the present invention is to provide a stator for an electric motor as mentioned at the outset, which has advantageous properties with regard to its manufacture and operation. This object is achieved by the features of the characterizing portion of claim 1. Advantageous embodiments of the invention are set out in the dependent claims. Summary of the Invention

[0004] The present invention relates to a stator for an electric motor, comprising a hollow cylindrical stator yoke and a star-shaped stator arranged within the stator yoke, the star-shaped stator having a plurality of stator teeth directed radially outward, the tips of which abut against corresponding connecting points on the inner circumferential surface of the stator yoke when assembled, the stator yoke and the star-shaped stator being each formed by a laminated core, the laminated core of the star-shaped stator including a metal sheet layer made of a stator metal sheet closed in the circumferential direction with the stator teeth connected to each other via pole shoe webs, and a metal sheet layer made of individual stator teeth spaced apart from each other in the circumferential direction.

[0005] It is proposed that the pole shoe webs each have at least one material recess extending in the radial direction.

[0006] The stator of the electric motor typically forms the stationary motor part of the electric motor, whereas the rotor of the electric motor forms the motor part of the electric motor which moves in rotation relative to the stator of the electric motor. In electric motors configured as inner rotor motors, the stator is usually provided with a stator yoke, on which stator teeth are arranged which project radially inwards towards the centre. The ends of the stator teeth facing the rotor each form a pole shoe. Stator windings are attached to the stator teeth which generate a magnetic field when the electric motor is in operation.

[0007] In order to make the stator teeth accessible from the outside for winding the stator windings on the stator teeth during production, and thus advantageously to achieve a high winding filling factor, the stator has a two-piece construction. The stator comprises a star-shaped stator with a number of stator teeth, each directed radially outward from a pole shoe. The stator further comprises a hollow cylindrical stator yoke. The stator yoke and the star-shaped stator are each formed by a punch-packed laminated core. The star-shaped stator and the stator yoke are each produced from individual stamped stator sheet metals, which are packed into a mechanically stable combination to form a sheet metal laminate. After the stator windings have been attached to the stator teeth of the star-shaped stator, the star-shaped stator provided with the stator windings is inserted into a stator yoke forming a return ring and joined to the stator yoke, in particular by pressing or shrinking. Before the star stator and the stator yoke are joined, the stator windings can be wound on the stator teeth, for example directly, for example by means of a flyer winding machine. In particular, the star stator has an electrically insulating coating with a layer thickness of up to 200 μm. In particular, the layer thickness of the coating can be between 100 μm and 200 μm. The coating can be applied to the star stator, in particular by electrophoretic deposition.

[0008] The stator yoke is in particular formed as a laminated core consisting of ring-shaped stator laminations. The star-shaped stator is formed by a laminated core with a number of radially extending stator teeth. Here, the laminated core of the star-shaped stator is formed from a circumferentially closed stator sheet metal with stator teeth connected to one another via pole shoe webs and a sheet metal layer consisting of individual stator teeth spaced apart from one another in the circumferential direction. A mechanically stable connection of the star-shaped stator is achieved by the sheet metal layer which comprises a circumferentially closed stator sheet metal with stator teeth connected to one another via pole shoe webs on the pole shoe side. The pole shoe webs of the circumferentially closed stator sheet metal of the star-shaped stator, which connect the pole shoes, each have at least one material recess extending in the radial direction. In particular, all pole shoe webs each have in particular the same material recess. In particular, each pole shoe web has one material recess. Due to the material recesses, the pole shoe webs each have a material reduction section, by means of which the magnetic flux between two adjacent pole shoes can advantageously be reduced via the pole shoe web connecting the pole shoes.

[0009] The material recess can in particular be provided in the pole shoe web after punching out the circumferentially closed stator sheet metal. Advantageously, however, the material recess is already provided in the pole shoe web when the circumferentially closed stator sheet metal of a star-shaped stator is punched out. In particular, the material recess is arranged in the pole shoe web on the rotor side. The material recess is in particular formed at least substantially in the shape of a circular arc. In particular, the material recess is formed at least substantially in the shape of a semicircle. Depending on the geometry of the material recess, in particular by forming the material recess in the shape of a circular arc, punching distortions in the region of the pole shoe web can at least be reduced or completely avoided.

[0010] In one embodiment of the invention, it is proposed that the material recesses are arranged in line with one another as viewed in the axial direction, which allows for an advantageously simple production of the stator, in particular of the star-shaped stator. Alternatively, the material recesses can be arranged offset with respect to one another as viewed in the axial direction, in particular in the form of so-called moving notches. By arranging the material recesses offset, an advantageous stiffness of the stator sheet metal of the star-shaped stator, which is closed in the circumferential direction, and thus of the entire star-shaped stator, can be achieved.

[0011] It is further proposed that the minimum radial material extension of the pole shoe web in the region of the material recess corresponds to 0.2 to 0.5 times the radial material extension of the pole shoe web outside the region of the material recess. Preferably, the minimum radial material extension of the pole shoe web in the region of the material recess corresponds to 0.3 to 0.4 times the radial material extension of the pole shoe web outside the region of the material recess. It is further proposed that the main extension of the material recess corresponds to at least 0.3 times the main extension of the respective pole shoe web. In this context, the "main extension" of an object is understood in particular to be the extension of the longest side of the smallest imaginary parallelepiped that exactly completely surrounds the object. Preferably, the main extension of the material recess corresponds to at least substantially 0.5 times the main extension of the respective pole shoe web. This makes it possible to achieve an advantageous material reduction of the pole shoe web while at the same time achieving a sufficient mechanical stability of the pole shoe web.

[0012] It is further proposed that the stator comprises an insulating element having a number of insulating strips arranged between the stator windings arranged on the stator teeth and the stator yoke in the assembled state. In the unassembled state, the insulating element is at least substantially radially shaped. In particular, the insulating element has a ring-shaped section, starting from which the insulating strips of the insulating element extend in the radial direction. The insulating element is provided in particular for electrically insulating the stator windings attached to the stator teeth from the stator yoke and / or for protecting the stator windings attached to the stator teeth from mechanical damage when the star stator is pressed against the stator yoke. Protecting the stator windings from mechanical damage is necessary in particular for high winding filling factors, in which the respective winding spaces between the stator teeth of the star stator are at least almost completely filled by the stator winding. "Provided" is understood in particular to mean specially designed and / or configured. An object is provided with a certain function, which is understood in particular if the object fulfills and / or performs the certain function in at least one application and / or operating state. The insulating element is formed in particular from an electrically insulating and flexible material, for example insulating paper or a plastic film, for example a polyimide film. Advantageously, the insulating element is formed in a one-sided self-adhesive manner. Before pressing the wound stator star onto the stator yoke, the insulating element is placed on the end side onto the stator winding. During pressing, the stator yoke causes a bending of the insulating strip, which contacts the stator winding between the stator teeth of the stator star. In this case, the mechanical load from the stator yoke acts only on the insulating element during pressing. After pressing, the insulating strip of the insulating element is located between the stator winding and the stator yoke and thus forms an electrical insulation between the stator winding and the stator yoke.

[0013] In particular, the stator is circumferentially encased by injection molding of plastic after the wound star stator is pressed onto the stator yoke. When encasing the stator by injection molding, the terminal ends of the stator windings must remain uncovered by plastic in order to be connected to the circuit board later. For this, the metallic terminal ends of the stator windings must be sealed during the encasing by injection molding. For this purpose, it is proposed that the stator contains a support element on the end side with a number of through holes for guiding the winding tips, which are provided for sealing the winding tips during the encasing by injection molding process. In addition, the support element serves to position the terminal ends of the stator windings on the circuit board. The support element is in particular at least substantially made of plastic. Before encasing the stator by injection molding, the support element is placed on the end side on the stator windings of the stator. The positioning of the support element takes place towards the stator by means of a molded positioning element. In this case, the terminal ends of the stator windings are inserted into the through-holes of the support element, the inner diameter of which at least substantially corresponds to the outer diameter of the terminal ends of the stator windings. In the region of the through-holes, the support element additionally has concentric circular ridges, which are provided for sealing the terminal ends of the stator windings in the injection molding tool. To position the circuit board in the stator, the support element has at least one positioning element, for example at least one pin, in particular a pin that is fixed by injection molding.

[0014] Here, the stator according to the present invention should not be limited to the above-mentioned applications and embodiments, in particular, the stator according to the present invention may have a number of individual elements, components and units different from the number described herein in order to fulfill the functions described herein.

[0015] drawing Further advantages will become apparent from the following description of the drawings, in which exemplary embodiments of the invention are shown. The drawings, the description and the claims contain a number of combinations of features which, preferably considered individually, will be combined by those skilled in the art into other useful combinations. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 shows an exploded view of a stator for an electric motor, comprising a hollow cylindrical stator yoke and a star-shaped stator. [Diagram 2] FIG. 2 is a perspective view of a stator yoke into which a star-shaped stator is press-fitted. [Diagram 3] A detailed view of the star stator is shown. [Figure 4] FIG. 2 shows another detailed view of the star stator. [Diagram 5] A cross-sectional view of the stator is shown. [Figure 6] FIG. 6 shows a detailed view of the cross-sectional view shown in FIG. 5. [Figure 7] 1 is a schematic diagram showing the offset between the punching position and the assembly position of the star-shaped stator. [Figure 8] FIG. 2 shows a perspective view of a stator with plastic injection molded around it. [Figure 9] 9 shows a cross-sectional view of the stator shown in FIG. 8 with a circuit board mounted thereon. [Figure 10] 13 shows a detailed cross-sectional view of an alternatively formed stator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] FIG. 1 shows an exploded view of a stator 10 for an electric motor formed as an internal rotor. The stator 10 comprises a hollow-tubular, e.g. hollow-cylindrical, stator yoke 12 and a star-shaped stator 14. In the assembled state shown in FIG. 2, the star-shaped stator 14 is arranged in the stator yoke 12. FIG. 5 shows a cross-sectional view of the assembled stator of FIG. 2, and FIG. 6 shows a detailed view of the cross-sectional view shown in FIG. 5. The star-shaped stator 14 can be joined to the stator yoke 12, in particular by pressing. The star-shaped stator 14 has a number of stator teeth 32 directed radially outward. Stator windings 54 are attached to the stator teeth 32 of the star-shaped stator 14. On the rotor side, the stator teeth 32 each have a pole shoe 68. Here, the star-shaped stator 14 exemplarily has 18 stator teeth 32. However, alternatively, the star-shaped stator 14 can also have a number of stator teeth 32 different from 18. In the assembled state, the tips 18 of the stator teeth 32 abut against corresponding connection points 20 on the inner circumferential surface of the stator yoke 12 (see Figures 5 and 6). The tips 18 of the stator teeth 32 have an interference with the connection points 20. The interference may be, for example, between 0.015 mm and 0.025 mm. The tips 18 of the stator teeth 32 are, in particular, rounded. The legs 80 of the tips 18 of the stator teeth 32 form an angle 82, in particular between 130° and 150°.

[0018] The stator yoke 12 and the star stator 14 are formed by punch-packed laminated cores 22, 24, respectively. The laminated core 22 of the stator yoke 12 includes a plurality of punch-packed ring-shaped stator metal sheets 66. The star stator 14 is formed by a laminated core 24 with stator teeth 32 directed radially outward. Here, the laminated core 24 of the star stator 14 includes a metal sheet layer 26 made of circumferentially closed stator metal sheets 28 with the stator teeth 32 connected to each other via pole shoe webs 30 (see FIG. 5). The pole shoe webs 30 extend between the pole shoes 68 of the adjacent stator teeth 32 of the circumferentially closed stator metal sheets 28, respectively (see FIGS. 5 and 6). Furthermore, the laminated core 24 of the star stator 14 includes a metal sheet layer 34 made of individual stator teeth 32 spaced apart from each other in the circumferential direction. Between two sheet metal layers 26 each consisting of a circumferentially closed stator sheet metal sheet 28 with stator teeth 32 connected to each other via a pole shoe web 30, a number of sheet metal layers 34 each consisting of individual stator teeth 32 spaced apart from each other in the circumferential direction are arranged. At the end sides, the laminated cores 24 of the star-shaped stator 14 are terminated by sheet metal layers 26 each consisting of a circumferentially closed stator sheet metal sheet 28. The punch packing of the laminated cores 22, 24 is preferably carried out in a common punch packing process. The stator sheet metal sheet 66 of the stator yoke 12 and the stator sheet metal sheet 28 or the individual stator teeth 32 of the star-shaped stator 14 are punched simultaneously, with the stator sheet metal sheet 28 or the individual stator teeth 32 of the star-shaped stator 14 being punched out inside the stator sheet metal sheet 66 of the stator yoke 12. In this regard, as shown in FIG. 7, the punching position 74 of the lamination core 24 of the star-shaped stator 14 is offset by a determined angle 78 with respect to the subsequent assembly position 76 of the lamination core 24 of the star-shaped stator 14 on the lamination core 22 of the stator yoke 12.In the illustrated example, the punching position 74 of the lamination core 24 of the star-shaped stator 14 is shifted by 10° with respect to the subsequent assembly position 76 of the lamination core 24 of the star-shaped stator 14 on the lamination core 22 of the stator yoke 12 .

[0019] The pole shoe webs 30 which connect the pole shoes 68 of the stator sheet metal 28 of the star-shaped stator 14, which are closed in the circumferential direction, each have at least one radially extending material recess 16. The material recesses 16 are arranged on the pole shoe web 30 on the rotor side, respectively. In the embodiment shown in FIG. 3, the material recesses 16 are arranged aligned with one another, viewed in the axial direction. Alternatively, as shown in FIG. 4, the material recesses 16 can be arranged offset with respect to one another, viewed in the axial direction. In particular, the material recesses 16 are arranged offset in opposite directions with respect to one another, as shown in FIG. 4, on opposite sides of the pole shoe 68. The material recesses 16 are formed in the shape of a circular arc. In the illustrated embodiment, the material recesses 16 are formed substantially in the shape of a semicircle. The minimum radial material extension 40 of the pole shoe web 30 in the region of the material recess 16 corresponds to 0.2 to 0.5 times the radial material extension 42 of the pole shoe web 30 outside the region of the material recess 16. Preferably, the minimum radial material extension 40 of the pole shoe web 30 in the region of the material recess 16 corresponds to 0.3 to 0.4 times the radial material extension 42 of the pole shoe web 30 outside the region of the material recess 16. Furthermore, the main extension 44 of the material recess 16 corresponds to at least 0.3 times the main extension 46 of each pole shoe web 30 (see FIG. 6). Preferably, the main extension 44 of the material recess 16 corresponds to at least substantially 0.5 times the main extension 46 of each pole shoe web 30.

[0020] Additionally, the stator 10 has an insulating element 48 with a number of insulating strips 50. As shown in FIG. 1, the insulating element 48 is at least substantially star-shaped or radially shaped in the illustrated non-assembled state. The insulating element 48 has a ring-shaped section 56, from which the insulating strips 50 of the insulating element 48 extend in the radial direction. The number of insulating strips 50 corresponds to the number of gaps 36 between the stator teeth 32. The insulating element 48 consists, inter alia, of an electrically insulating and flexible material, for example insulating paper or a polyimide film. The insulating element 48 is provided in order to protect the stator windings 54 attached to the stator teeth 32 from mechanical damage when the star-shaped stator 14 is pressed against the stator yoke 12 after the stator windings 54 have been electrically insulated from the stator yoke 12. Before the wound star stator 14 is inserted into the stator yoke 12, the insulating element 48 is applied on the end side to the stator winding 54. Advantageously, the insulating element 48 is self-adhesive on one side, at least in the region of the ring-shaped section 56, so that the insulating element 48 can be advantageously pre-fixed to the stator winding 54. When pressed, the insulating strip 50 is folded by the stator yoke 12 in the direction of movement of the stator yoke 12. This folding causes the insulating strip 50 to rest on the stator winding 54 between the stator teeth 32 of the star stator 14. The mechanical loads imposed by the stator yoke 12 during insertion therefore only act on the insulating strip 50 of the insulating element 48. As a result, in the assembled state of the stator 10, the insulating strip 50 is arranged between the stator winding 54 arranged on the stator teeth 32 and the stator yoke 12, as can be seen in particular from FIGS. 5 and 6.

[0021] In particular, after the wound star stator 14 is pressed onto the stator yoke 12, plastic is injection molded around the stator 10. Such an injection molded stator 10 is shown in FIGS. 8 and 9. When the stator 10 is injection molded, the terminal ends 62 of the stator windings 54 must remain uncovered by the plastic for connection to the circuit board 64. In order to seal the terminal ends 62 of the stator windings 54 against the cavity of the injection mold tool during the injection molding process, the stator 10 has a support element 58 on the end side. Besides the sealing purpose, the support element 58 also serves to align the terminal ends 62 of the stator windings 54 against the circuit board 64. The support element 58 is made of, in particular, plastic. The support element 58 has a number of through holes 60 for guiding the terminal ends 62 of the stator windings 54. The support element 58 is placed on the stator windings 54 at the end side before being wrapped around the stator 10 by injection molding. The positioning of the support element 58 is performed here by means of the positioning element 52 molded on the support element 58. For positioning the support element 58 in the circumferential direction, the support element 58 has, for example, at least one pin which engages in a corresponding recess in the star stator 14. In particular, the support element 58 can have a number of pins arranged in the circumferential direction, which engage in a corresponding number of recesses in the star stator 14. Alternatively or additionally, the positioning of the support element 58 in the circumferential direction can be performed by other suitable means. For example, the support element 58 can have positioning elements, not shown here, which directly interact with the winding heads of the star stator 14 for positioning the support element 58 in the circumferential direction.

[0022] The terminal ends 62 of the stator windings 54 are inserted into the through-holes 60 of the support element 58 when the support element 58 is placed and guided through the through-holes 60. The inner diameter of the through-holes 60 corresponds at least substantially to the outer diameter of the terminal ends 62 of the stator windings 54, so that at least a sufficient, in particular complete, sealing is achieved over the outer circumference of the terminal ends 62 against plastic entering from the cavity of the injection molding tool in the direction of the terminal ends 62 during the injection molding around the stator 10. In the region of the through-holes 60, the support element 58 additionally has concentric ridges 72. The terminal ends 62 are inserted into recesses in the injection molding tool, which are sealed by the ridges 72 in the direction of the cavity of the injection molding tool. Thus, the inflow of plastic into the recesses into which the terminal ends 62 are inserted can be advantageously avoided.

[0023] After the stator 10 has been circumferentially molded by injection molding, a circuit board 64 is placed on the support element 58. The circuit board 64 is circular and, in the assembled state, rests on the support element 58 at its end side (see FIG. 9). The circuit board 64 is provided for the electrical connection of the stator windings 54. For this purpose, the terminal ends 62 of the stator windings 54 are electrically conductively connected to the circuit board 64, in particular by means of solder connections. For the positioning of the circuit board 64 on the support element 58, the support element 58 has axially extending pins 70 which correspond to the recesses 38 of the circuit board 64.

[0024] FIG. 10 shows a detailed cross-section of an alternatively formed stator 10 with a star stator 14 and a stator yoke 12. The star stator 14 can be joined to the stator yoke 12, in particular by pressing. The star stator 14 has a number of stator teeth 32 directed radially outwards. Stator windings 54 are attached to the stator teeth 32 of the star stator 14. On the rotor side, the stator teeth 32 each have a pole shoe 68. In the assembled state, the tips 18 of the stator teeth 32 abut against corresponding connection points 20 on the inner circumference of the stator yoke 12. The tips 18 of the stator teeth 32 are in particular rounded. In the embodiment of FIG. 6, the tips 18 of the stator teeth 32 have a corresponding arc-shaped geometry on the outer circumference of the star stator 14 in the direction of the stator yoke 12. [Explanation of symbols]

[0025] 10 Stator 12 Stator yoke 14 Star Stator 16 Material recess 18 Tip 20 Connection points 22 Laminated Core 24 Laminated Core 26 thin metal layer 28 Stator metal sheet 30 Pole Shoe Web 32 Status Teeth 34 Metal thin plate layer 36 Gap 38 Recess 40 Material extension 42 Material extension 44 Main extension 46 Main extension 48 Insulating Element 50 Insulating strip 52 Positioning elements 54 Stator Winding 56 Sections 58 Support element 60 Through Hole 62 Terminal end 64 Circuit Board 66 Stator metal sheet 68 Pole shoe 70 pin 72 Ridge 74 Punching position 76 Installation position 78 angle 80 Legs 82 angle

Claims

1. A stator for an electric motor, comprising: a hollow cylindrical stator yoke (12); and a star-shaped stator (14) disposed within the stator yoke (12), a stator for an electric motor, the stator having a plurality of stator teeth directed radially outward, tips of the stator teeth being in abutment with corresponding connecting points on an inner circumferential surface of the stator yoke in an assembled state, the stator yoke and the star stator being formed by laminated cores, the laminated cores of the star stator including a sheet metal layer made of a circumferentially closed stator sheet metal layer having stator teeth connected to one another via pole shoe webs, and a sheet metal layer made of individual stator teeth spaced apart from one another in the circumferential direction, the pole shoe webs (30) each have at least one material recess (16) extending in the radial direction, and a metal sheet layer (26) made of a stator metal sheet (28) closed in the circumferential direction has the material recess (16) and a material extension outside the area of ​​the material recess (16); a material extension portion outside the area of ​​the material recess (16) extends from the stator tooth (32) and is disposed between the stator tooth (32) and the material recess (16); A stator for an electric motor comprising:

2. 2. The stator according to claim 1, characterized in that the material recess (16) is formed at least substantially in the shape of a circular arc.

3. 3. A stator according to claim 1 or 2, characterized in that the material recesses (16) are respectively arranged in the pole shoe webs (30) on the rotor side.

4. 4. A stator according to claim 1, wherein the material recesses (16) are arranged in mutual alignment as viewed in the axial direction (38).

5. 4. A stator according to claim 1, wherein the material recesses (16) are arranged offset relative to one another in the axial direction (38).

6. 6. A stator according to claim 1, characterized in that the minimum radial material extension (40) of the pole shoe web (30) in the region of the material recess (16) corresponds to 0.2 to 0.5 times the radial material extension (42) of the pole shoe web (30) outside the region of the material recess (16).

7. 7. A stator according to claim 1, wherein the main extension (44) of the material recess (16) corresponds to at least 0.3 times the main extension (46) of each pole shoe web (30), respectively.

8. 8. The stator according to claim 1, further comprising an insulating element having a plurality of insulating strips arranged between the stator windings arranged on the stator teeth and the stator yoke when the stator is assembled.

9. 9. A stator according to claim 8, characterized in that the insulating element (48) has a ring-shaped section (56), starting from which the insulating strips (50) of the insulating element (48) extend in a radial direction.

10. 10. The stator according to claim 1, further comprising end support elements (58) with a number of through holes (60) for guiding terminal ends (62) of the stator windings (54), the support elements (58) being provided for sealing the terminal ends (62) of the stator windings (54) during the injection molding encircling process.

11. A size of a minimum radial material extension (40) of the pole shoe web (30) in the region of the material recess (16) is smaller than a size of a minimum radial material extension (42) of the pole shoe web (30) outside the region of the material recess (16). A stator according to any one of claims 1 to 10.

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