Rotor for an electrical machine, electrical machine and method for producing a rotor for an electrical machine

Abstract

In order to improve the cross-section of the laminations of a laminated core of a rotor in such a way that the efficiency is optimized and that production is simplified, a rotor (100) for an electrical machine (200), in particular for an asynchronous machine, is proposed, comprising a laminated core (13) comprising a plurality of laminations (14), each lamination (14) having a sheet thickness, the laminated core (13) comprising at least one groove (15), the groove (15) having a receiving area (16) for receiving a short-circuit bar (17), the laminated core (13) having a cavity (19) separated from the groove (15) in the radially outer direction by a first scattering web (18), the first scattering web (18) being curved, the cavity (19) being closed in the radially outer direction by a second scattering web (20), further providingthat the cavity (19) has circular segment-shaped end regions (22) in a circumferential direction (21) of the laminated core (13).

Description

Owing to the additionally induced excitation of the rotor field, asynchronous machines usually have a lower efficiency than permanent magnet excited synchronous machines. For example, EP 2 999 100 B1 shows a method for producing a cage rotor, while DE 10 2016 124 830 A1 relates to a sheet metal for forming a laminated core for a rotor of an electric machine. JP H 09224358 A and JP 59106865 A2 also show cross sections of corresponding rotor blades.Decisive for the efficiency or the efficiency of an asynchronous machine are the specific design of the rotor lamination section and the geometric relationships of the dimensions to one another.The present invention is based on the object of improving the cross section of the sheets of a laminated core of a rotor in such a way that the efficiency is optimized and that the production is simplified.To achieve the object underlying the invention, a rotor for an electric machine, in particular for an asynchronous machine, is proposed, comprising a laminated core comprising a plurality of sheets, wherein each sheet has a sheet thickness, wherein the laminated core comprises at least one groove, wherein the groove has a receiving region for receiving a short-circuiting rod, wherein the laminated core has a cavity which is separated from the groove in the radially outer direction by a first spreading web, wherein the first spreading web is formed in a curved manner, wherein the cavity is closed in the radially outer direction by a second spreading web, wherein it is further provided that the cavity has end regions which are in the form of a circular segment at the end in a circumferential direction of the laminated core.The laminated core preferably has a plurality of grooves. In particular, each sheet metal of the laminated core comprises at least one groove, wherein the sheets are stacked in the axial direction such that the groove of the laminated core is formed over the entire thickness or axial length of the laminated core.The at least one groove has a receiving region for receiving a respective short-circuit rod. In this case, it can be provided that the receiving region is completely filled by the short-circuit rod when a short-circuit rod is received. Viewed radially outwards, the groove, or in the case of a plurality of grooves each groove, is assigned a respective cavity. The cavity is separated from the respective groove by a first scattering web. The spreading web is curved in this case. The cavity is closed in the radially outer direction by a second scattering web. The radially outer edge of the second diffusion web is here part of the outer line of the rotor or of the laminated core. The cavity can thus be bounded in the radially inner direction by the first scattering web and in the radially outer direction by the second scattering web.The cavity has an extent as seen in a circumferential direction of the laminated core, wherein the cavity has end regions in the form of circular segments as seen in the circumferential direction of the laminated core.This means in particular that a boundary of the cavity in the end regions is substantially circular-arc-shaped, or is formed by a plurality of circular-arc-shaped sections. The end regions formed in the shape of a circular segment result in a rounding of the boundary of the cavity in the end regions to a certain extent. The rotor is therefore simple to produce, in particular simple to cast, and the tool durability, in particular that of punching presses, can be increased by a multiple.It is preferably provided that the sheet thickness is between 0.15 and 0.35 mm.It is preferably further provided that each of the circular-segment-shaped end regions comprises an outer segment having a first radius of curvature in the radial direction and an inner segment having a second radius of curvature adjoining the first segment in the radial direction.In other words, the boundary of the end regions can have a varying radius of curvature over the course of the boundary.In this case, it can be provided in particular that the first radius of curvature and / or the second radius of curvature is 0.5 times to 4.0 times the sheet thickness.In principle, it is possible for the first radius of curvature and the second radius of curvature to be the same. However, it is preferred that the first radius of curvature and the second radius of curvature are different.If the first radius of curvature and the second radius of curvature are different, the boundary of the end regions has a varying radius of curvature. In particular, it can be provided that the first radius of curvature of the boundary of the portion of the end region situated further outward as viewed in the radial direction is greater than the second radius of curvature of the boundary of the portion of the end region situated further inward as viewed in the radial direction.It can be provided with further advantage that the groove in the receiving region comprises a maximum width, wherein the maximum width is preferably between 2 mm and 7 mm, and that the cavity has a width, wherein the width of the cavity is greater than or equal to the maximum width of the receiving region.The maximum width of the receiving region or the width of the cavity is preferably measured in the circumferential direction of the rotor lamination.The first scattering web can have a constant width. The second spreading web can also have a constant width or a different or varying width. For example, the width of the second scattering web can be greater or smaller in a central section with respect to the width of the cavity than in a section in the region of the end regions.In particular, it can be provided that the first spreading web has a width between 0.5 times to 3.0 times the sheet thickness, and / or that the second spreading web has a width between 0.5 times to 2.5 times the sheet thickness.The width of the receiving region can increase continuously in the radial direction, in particular from a radially inner region, up to the location of the maximum width of the receiving region. In this case, it can preferably be provided that the receiving region has a semicircular end region arranged in the radially outer direction and having a third radius of curvature, wherein the third radius of curvature is preferably 0.2 times to 0.9 times, preferably 0.3 times to 0.7 times, the maximum width. In other words, at the location at which the maximum width of the receiving region occurs, a semicircular end region of the receiving region can adjoin. The approximately semicircular end region can also have a slightly varying radius of curvature. Thus, the width of the receiving region decreases in the radially outer direction starting from the location of the maximum width corresponding to the circular geometry of the semicircle.A corresponding semicircular end region can also be provided at the radially inner end of the receiving region or of the groove. In addition to the maximum width, the receiving region can have a minimum width at the radially inner end of the receiving region, wherein the semicircular end region can adjoin the location of the minimum width at the radially inner end of the receiving region. The minimum width can be between 0.35 and 0.65 times the maximum width. The minimum width thus does not relate to the semicircular end region at the radially inner end of the receiving region, in which the width of the corresponding circular geometry naturally decreases further.The length of the receiving region relates in particular to the distance between the location of the maximum width and the location of the minimum width, wherein the length of the receiving region is between 9 mm and 49 mm or 4.5 to 7 times the maximum width.The rotor has in particular a radius, wherein the rotor radius can correspond to 2 to 4 times the length of the receiving region.It is preferably provided that the cavity has a radially inner boundary with a fourth radius of curvature, wherein the fourth radius of curvature, preferably measured from a center of the semicircular end region of the receiving region, is 0.9 times to 1.2 times the third radius of curvature.A further solution to the object on which the invention is based is to provide an electric machine comprising a rotor described above.Yet another solution of the object underlying the invention is to provide a method for producing a rotor for an electric machine, in particular for an asynchronous machine, more particularly for a rotor described above, comprising a laminated core comprising a plurality of sheets, wherein the method comprises producing at least one radially extending groove of the laminated core, wherein the groove has a receiving region for receiving a short-circuiting rod, wherein the laminated core has a cavity which is separated from the groove in the radially outer direction by a first spreading web, wherein the first spreading web is formed in a curved manner, wherein the cavity is closed in the radially outer direction by a second spreading web, and wherein the cavity has end regions in the form of a circular segment in a circumferential direction of the laminated core.In particular, the sheets can be cast while the corresponding groove is filled by means of a filling material, for example by a gypsum material, prior to casting the rotor.Furthermore, it is also possible for the grooves and the cavities to be produced by means of a punching tool after the casting of the rotor or of the metal sheets. The sheets can then be laminated to form a laminated core and oriented in such a way that the grooves lie on one another with an exact fit in the axial direction.Furthermore, the short-circuit bars can be cast, namely in the respective receiving regions. The method can thus comprise pouring a material for forming short-circuit bars into the receiving region of the at least one groove. The material can be, in particular, copper and / or aluminum and / or silver.Instead of casting the short-circuit bars, the short-circuit bars can also be used, for which purpose they are produced separately beforehand.The invention is explained in more detail below with reference to the attached figures. They are shown in a purely schematic illustration FIG. 1 shows a cross section of a rotor of an electric machine, FIG. 2 shows an enlarged view of a detail from FIG. 1, FIG. 3 is an enlarged view of a detail of FIG. 1 ; and FIG. 4 shows a process diagram of a method for producing a rotor.In FIG. 1, a rotor 100 in an electric machine 200 is shown. In addition to the rotor 100, the electric machine 200 has a stator 10 with slots 11 which is arranged over the full circumference around the rotor 100. A gap 12 is located between the rotor 100 and the stator 10. The rotor 100 comprises a laminated core 13 which consists of laminations 14 stacked one on top of the other in the axial direction, of which a lamination 14 can be seen in a plan view in FIG. 1. The sheet thickness of each sheet 14 may be between 0.15 mm and 0.35 mm. The metal sheet 14 has radially extending grooves 15, wherein the grooves 15 each have a receiving region 16 for receiving a short-circuiting rod 17. As seen in a radially outer direction, as shown in particular in FIG. 2, there is a cavity 19 which is separated from the groove 15 by a first spreading web 18. The cavity 19 is closed in the radially outer direction by a second scattering web 20. As can be seen in particular in FIG. 1, each groove 15 is assigned a corresponding cavity 19. Each of the cavities 19 has end regions 22 in the form of a segment of a circle, as seen in a circumferential direction 21 of the laminated core 13. Each of the circular-segment-shaped end regions 22 has an outer segment 23 in the radial direction with a first radius of curvature 24, and an inner segment 25 adjoining the first segment 23 in the radial direction with a second radius of curvature 26. The first radius of curvature 24 and the second radius of curvature 26 are between 0.5 times to 4.0 times the sheet thickness. As illustrated, in particular, the second radius of curvature 26 may be less than the first radius of curvature 24. The first radius of curvature 24 and the second radius of curvature 26 are thus different. The grooves 15 have a maximum width 27 in the receiving region 16, which is between 2 mm and 7 mm. The cavity 19 accordingly likewise has a width 28 viewed over the circumferential direction 21 of the laminated core 13, wherein the width 28 of the cavity 19 is greater than that of the maximum width 27 of the receiving region 16. The first spreading web 18 has a width 29 between 0.5 times to 3.0 times the sheet thickness, and the second spreading web 20 has a width 30 between 0.5 times to 2.5 times the sheet thickness. The receiving region 16 has a semicircular end region 31 arranged in the radially outer direction, with a third radius of curvature 32, which lies between 0.3 times and 0.7 times the maximum width 27 of the receiving region 16.As can be seen in particular from FIG. 3, the receiving region 16 also has a minimum width 33 located in the radially inner region of the rotor stack 13. The width of the receiving region 16 thus increases continuously from the radially inner region of the receiving region 16 to the radially outer region of the receiving region 16 until the maximum width 27 is reached. The receiving region 16 also comprises a semicircular end region 34 arranged in the radially inner direction. The receiving region 16 extends between the location of the maximum width 27 and the location of the minimum width 33 over a length 35 which is between 4.5 times to 7 times the maximum width 27.FIG. 4 shows a method diagram of a method 300 for producing a rotor 100. In a first step S 1, metal sheets 14 can be produced. In this case, grooves 15 are provided which have a receiving region 16. Furthermore, cavities 19 are provided in the metal sheets 14, which cavities are separated from the grooves 15 by a first spreading web 18. The sheets 14 can be laminated and aligned in a second method step S 2 to form a laminated core 13. A short-circuit rod 17 can now be introduced in a third method step S 3.List of reference characters100 Rotor 200 Electric machine 300 Method 10 Stator 11 Groove 12 Gap 13 Laminated core 14 Sheet 15 Groove 16 Receiving region 17 Short-circuit rod 18 First scattering web 19 Cavity 20 Second scattering web 21 Circumferential direction 22 Circular-section-shaped end region 23 Outer section 24 First radius of curvature 25 Inner section 26 Second radius of curvature 27 Maximum width 28 Width 29 Width 30 Width 31 Semicircular end region 32 Third radius of curvature 33 Minimum width 34 Semicircular end region 35 Length S 1 Method step S 2 Method step S 3 Method stepReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedEP 2 999 100 B1

[0001] DE 10 2016 124 830 A1

[0001] JP H 09224358

[0001] JP 59106865 A2

[0001]

Claims

Rotor (100) for an electric machine (200), in particular for an asynchronous machine, comprising a laminated core (13) comprising a plurality of sheets (14), wherein each sheet (14) has a sheet thickness, wherein the laminated core (13) comprises at least one groove (15), wherein the groove (15) has a receiving region (16) for receiving a short-circuiting rod (17), wherein the laminated core (13) has a cavity (19) which is separated from the groove (15) in the radially outer direction by a first spreading web (18), wherein the first spreading web (18) is formed in a curved manner, wherein the cavity (19) is closed in the radially outer direction by a second spreading web (20), characterized in that the cavity (19) has end regions (22) which are in the form of a circular segment at the end in a circumferential direction (21) of the laminated core (13).Rotor (100) according to Claim 1, characterized in that the sheet thickness is between 0.15 mm and 0.35 mm.Rotor (100) according to Claim 1 or 2, characterized in that each of the end regions (22) in the form of a segment of a circle comprises an outer portion (23) with a first radius of curvature (24) in the radial direction and an inner portion (25) with a second radius of curvature (26) adjoining the first portion (23) in the radial direction.Rotor (100) according to claim 3, characterised in that the first radius of curvature (24) and / or the second radius of curvature (26) is 0.5 to 4.0 times the sheet thickness.Rotor (100) according to claim 3 or 4, characterised in that the first radius of curvature (24) and the second radius of curvature (26) are different or equal.Rotor (100) according to one of the preceding claims, characterized in that the groove (15) in the receiving region (16) comprises a maximum width (27), wherein the maximum width (27) is preferably between 2 mm and 7 mm, and in that the cavity (19) has a width (28), wherein the width (28) of the cavity (19) is greater than or equal to the maximum width (27) of the receiving region (16).Rotor (100) according to one of the preceding claims, characterized in that the first spreading web (18) has a width (29) between 0.5 times to 3.0 times the sheet thickness, and / or in that the second spreading web (20) has a width (30) between 0.5 times to 2.5 times the sheet thickness.Rotor (100) according to one of the preceding claims, characterized in that the receiving region (16) has a semicircular end region (31), which is arranged in the radially outer direction and has a third radius of curvature (32), wherein the third radius of curvature (32) is preferably 0.2 times to 0.9 times, preferably 0.3 times to 0.7 times, the maximum width (27).Electric machine (200) comprising a rotor (100) according to any one of claims 1 to 8.Method (300) for producing a rotor (100) for an electric machine (200), in particular for an asynchronous machine, in particular according to one of Claims 1 to 8, comprising a laminated core (13) comprising a plurality of sheets (14), wherein the method comprises producing at least one radially running groove (15) of the laminated core (13), wherein the groove (15) has a receiving region (16) for receiving a short-circuiting rod (17), wherein the laminated core (13) has a cavity (19) which is separated from the groove (15) in the radially outer direction by a first spreading web (18), wherein the first spreading web (18) is of curved design, wherein the cavity (19) is closed in the radially outer direction by a second spreading web (20), and wherein the cavity (19) has end regions (22) which are in the form of a segment of a circle at the end in a circumferential direction (21) of the laminated core (13).

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