Method for producing a sheet metal part

Abstract

The invention relates to a method for producing a sheet metal part (1) for a laminated core (2) of a rotor (3) of an electric motor (4), the sheet metal part having at least two recesses (5) and at least two rotor webs (6a, 6b, 6c), wherein the sheet metal part (1) is punched from a sheet metal strip. In order to impart a high strength to the laminated core (2) formed from a plurality of sheet metal parts (1), it is provided that the sheet metal part (1) is formed in at least one region (7) such that a positive or negative bulge (9) is produced relative to the sheet metal part plane (8).

Description

Technical Field

[0001] The invention relates to a method for producing a sheet metal part for a laminated core of a rotor of an electric motor according to the preamble of claim 1. Furthermore, the invention relates to a sheet metal part produced according to the method and to a rotor of an electric motor having a plurality of such sheet metal parts, which are stacked on top of one another and connected to one another. Background Art

[0002] DE 10 2018 107 916 A1 discloses a general method for producing a sheet metal part for a laminated core of a rotor for an electric motor, the sheet metal part having at least two recesses and at least two rotor webs. According to the method, the sheet metal part is punched from a sheet metal strip. In this process, the sheet metal part to be punched is positioned between a punch and an associated die of a punching tool. Subsequently, a relative movement occurs between the punch and the die, causing the sheet metal part to be punched. After the relative movement between the punch and the die required for punching has been completed, the sheet metal part is cold-formed in selected areas of the sheet metal part for the purpose of reducing the magnetic permeability, since forces act on the sheet metal part held between the punch and the die in these areas. Further relative movements between the punch and the die occur in the further process to remove the punched sheet metal part from the punching tool.

[0003] The production of sheet metal parts by stamping and the local compression of such parts, for example to increase mechanical strength or reduce magnetic permeability, are already known. In this process, individual sheet metal parts are punched from a sheet metal strip and additionally compacted, for example at the edges of a recess through which a wire or magnet can then be passed. The resulting web in the circumferential direction or between two recesses should be as thin as possible to minimize stray magnetic fields, but must not fall below a certain thickness due to strength requirements. Summary of the Invention

[0004] The object of the present invention is therefore to provide an improved or at least alternative embodiment for a method of the generic type, with which sheet metal parts having a higher strength can in particular be produced.

[0005] According to the invention, this problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0006] The present invention is based on the following general idea: Instead of forming sheet metal parts used to assemble rotors for electric motors flat, sheet metal parts are formed with at least one region outside their plane, particularly in the region of the rotor webs. This increases the strength of the sheet metal parts and reduces stray magnetic fields, for example, that occur in these regions. In the method according to the present invention for producing a sheet metal part for a laminated core of a rotor for an electric motor, the sheet metal part comprises at least two recesses and at least two rotor webs and is stamped from a flat sheet metal strip. During or after stamping, the sheet metal part is formed in at least one region to produce a bulge that protrudes from the plane of the sheet metal part, thereby giving the sheet metal part, previously formed only in a flat manner, a three-dimensional shape. The present invention thus utilizes the principle of three-dimensional forming. This three-dimensional shaping increases strength, which in turn enables higher speeds and higher power, particularly for electric motors equipped with such rotors. The bulge can be formed as either a positive bulge or a negative bulge, with the negative bulge protruding on the opposite side of the sheet metal part.

[0007] In an advantageous further development of the method according to the invention, at least two rotor webs are formed to form connections to the protuberances, which protrude obliquely from the plane of the sheet metal part. In this process, the rotor webs are lengthened and plasticized without changing the outer diameter of the sheet metal part. Plasticization increases the strength of the rotor webs, thereby improving speed stability. Furthermore, the magnetic permeability in the region of the rotor webs is reduced, thereby reducing stray fields and, in turn, increasing torque.

[0008] In another advantageous embodiment of the method according to the invention, the formed ridge is connected to the sheet metal plane via three rotor webs, wherein the ridge forms a plane parallel to the sheet metal plane. This allows, for example, a single flat region spaced parallel to the actual component plane to be arranged via three rotor webs, thereby achieving relatively simple forming. The parallel planes of the ridge and the sheet metal plane also enable planar joining of multiple sheet metal parts to form the laminated core of an electric motor rotor.

[0009] In another advantageous embodiment of the method according to the invention, one of the three rotor webs extends radially of the sheet metal part to a projection formed by parallel planes, while two rotor webs are arranged in the outer circumferential region. This makes it possible, for example, to limit radially outward depressions, with centrifugal forces acting on the parallel planes being absorbed by the radially extending rotor webs.

[0010] In another advantageous embodiment of the method according to the invention, at least one shaped region is formed in the form of an at least partially annular channel or bead. Such a channel or bead can have, for example, a circular, triangular, or trapezoidal cross-section. The raised portion or channel formed in this manner can also increase the component strength and rigidity of the sheet metal part, thereby enabling higher speeds in electric motors equipped with such a sheet metal part. Furthermore, a higher reluctance torque can be achieved. The higher reluctance torque is a portion of the torque generated by the magnetic attraction of the iron core. The rotor web reduces this portion of torque. The smaller the rotor web, the greater the reluctance torque that can be achieved. Therefore, the method is also very suitable for synchronous reluctance motors that do not have any magnets or coils in the rotor and utilize only the reluctance torque generated by the iron rotor.

[0011] In another advantageous embodiment of the method according to the invention, the sheet metal part is compressed during or after forming, in particular in the radial direction. Compression can also introduce residual compressive stresses, which in turn can increase the rotational speed, since these residual compressive stresses must first be removed in order to introduce tensile stresses into the component.

[0012] Furthermore, the present invention is based on the following general idea: a sheet metal part manufactured according to the method described in the preceding paragraphs is used in a rotor for an electric motor, wherein a plurality of such sheet metal parts are stacked on top of one another and connected to one another. In this way, the advantages described above with respect to a single sheet metal part can be accumulated, so that a rotor for an electric motor manufactured from such sheet metal parts not only has increased strength due to, for example, applied residual compressive stresses, but also can accommodate magnets of the same size, for example, with reduced material usage, thereby enabling higher torques to be achieved while using the same magnet material.

[0013] Further important features and advantages of the invention can be gathered from the dependent claims, from the drawings and from the associated description of the figures via the drawings.

[0014] It is understood that the features mentioned above and still to be explained below can be used not only in the respective combination stated but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] BRIEF DESCRIPTION OF THE DRAWINGS Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in detail in the following description, wherein identical reference numerals designate identical or similar or functionally identical components.

[0016] In each case schematically shown,

[0017] Figure 1 shows an excerpt of a sheet metal part of a laminated core for an electric motor rotor in a first embodiment according to the invention,

[0018] Figure 2 shows an excerpt of a laminated core of a rotor of an electric motor made from a plurality of sheet metal parts according to the invention,

[0019] Figure 3 Different views showing another possible embodiment of the sheet metal part according to the invention,

[0020] Figures 4 to 6 Shows their respective Figure 3 Similar but each in a different embodiment. DETAILED DESCRIPTION

[0021] according to Figures 1 to 6 , according to the present invention, a laminated core 2 for a rotor 3 of an electric motor 4 (see Figure 2 ) comprises at least two recesses 5 for the magnets and at least two rotor webs 6a, 6b, and 6c. The sheet metal part 1 according to the invention is initially stamped from a flat sheet metal strip and, during or after stamping, is formed in at least one region 7, resulting in a bulge 9 protruding from the sheet metal plane 8. As described herein, this bulge 9 can have many different embodiments and can also be negative.

[0022] For example, observations based on Figure 1 and Figure 2 In the embodiment of the sheet metal part 1 of FIG. 1 , the rotor webs 6 a, 6 b and 6 c are formed such that they form a connection to the bulge 9 protruding obliquely from the sheet metal part plane 8. In this case, the bulge 9 lies in a plane spaced apart parallel to the sheet metal part plane 8.

[0023] The rotor webs 6a, 6b, and 6c, which protrude obliquely from the sheet metal plane 8 and the ridges 9, reinforce the entire sheet metal part 1, thereby enabling higher speeds. The oblique orientation of the rotor webs 6a, 6b, and 6c also influences the magnetic properties, as they are lengthened and plasticized without changing the outer diameter of the sheet metal part 1. Plasticization increases the strength of the rotor webs 6a, 6b, and 6c, leading to improved speed stability. Furthermore, the magnetic permeability in the region of the rotor webs 6a, 6b, and 6c decreases, and stray fields are reduced as a result, resulting in increased torque.

[0024] Further observation Figure 1 and Figure 2 as well as Figures 3 to 6It is noteworthy that the rotor web 6a extends in the radial direction 10 of the sheet metal part 1, while the two rotor webs 6b and 6c are arranged in the outer circumferential region and respectively extend in the circumferential direction 11. The rotor webs 6a, 6b and 6a and 6c, as well as the sheet metal part 1 in the component plane 8 and the sheet metal part 1 in the elevation 9, delimit a recess 5 in which, for example, a magnet or a coil wire is arranged.

[0025] according to Figure 3 a and Figure 3 The sheet metal component 1 of FIG. 1 includes rotor webs 6a, 6b, and 6c located in the component plane 8. At least one formed region 7 is formed in the form of an at least partially annular channel 12 having a triangular cross-section. This channel 12 is a bead, viewed from the other side. This allows for bead-like hardening of the sheet metal component 1, which also results in increased stiffness. The channel 12 increases the stiffness of the rotor 3. The presence of the channel 12, or generally the bead, serves to introduce compressive stresses into the rotor webs 6a, 6b, 6c, thereby increasing speed stability.

[0026] Observation basis Figure 4 The sheet metal part 1 shown further comprises a channel 12 as a shaped region 7 (negative bulge 9), wherein the radial extent of the channel 12 is significantly greater than that according to Figure 3 、 Figure 5 or Figure 6 The radial extent of the channel 12. Here, the recess 5 also runs obliquely to the radial direction 10.

[0027] In accordance with Figure 5 a and Figure 5 In the sheet metal part of b, it can also be noted that the shaped area 7 is in the form of a partial annular channel 12, which is located radially inside the recess, unlike according to Figure 3 and Figure 4 The region 7 of the sheet metal part 1 is passed through the recess 5. Figure 5 a and Figure 5 The channel 12 of b has a circular cross section or channel bottom.

[0028] In accordance with Figure 6 a and Figure 6 On sheet metal component 1 of FIG. b, two shaped regions 7 can be seen, spaced apart from one another in the radial direction. The radially outer region 7 also includes a channel 12, but with a trapezoidal cross-section. This channel 12 also extends through recess 5. However, recess 5 also extends into a central region 13, which is located at the level of component plane 8. Radially within central region 13, shaped region 7 can again be seen. This shaped region merges from central region 13 into radially inner region 15 via an inclined surface 14.

[0029] In addition to forming substantially perpendicularly to the component plane 8 to produce the bulge 9 (which, at the opposite angle, can obviously also represent a depression), the sheet metal component 1 can also be compressed during or after forming (in particular, against the radial direction 10), with residual compressive stresses being applied to the sheet metal component 1, which in turn increases the component strength. During the rotation of the rotor 3, the residual compressive stresses applied against the radial direction 10 must be compensated by centrifugal forces in order to subsequently apply tensile forces to the sheet metal component 1.

[0030] The sheet metal part 1 can be manufactured relatively easily by stamping and forming. The advantages achieved by forming the region 7 and creating the ridges 9 are remarkable. These advantages are, in particular, increased strength and rigidity, as well as reduced magnetic permeability in the region of the rotor webs 6a, 6b, 6c. The increased strength allows for higher rotor speeds with the same web dimensions, or for smaller web dimensions to be used at the same speed, thereby increasing torque or reducing the amount of magnet material required.

[0031] In this Figures 1 to 6 In the case where only a metal sheet 1 in the form of a circle segment is shown but is generally formed into a disk shape and a circle shape, the advantages described for a single metal sheet 1 can also be applied to a rotor 2 equipped with such a metal sheet 1 and an electric motor 3 equipped with such a rotor 2.

Claims

1. A method for producing a sheet metal part (1) for a laminated core (2) of a rotor (3) of an electric motor (4), the sheet metal part having at least two recesses (5) and at least two rotor webs (6a, 6b, 6c), wherein the sheet metal part (1) is stamped from a sheet metal strip, It is characterized in that The sheet metal part (1) is shaped in at least one region (7) such that a bulge (9) is produced relative to the sheet metal part plane (8). At least one shaped area (7) is formed in the form of an at least partially annular channel (12), and The cross section of the channel (12) is circular, triangular or trapezoidal.

2. The method according to claim 1, It is characterized in that The at least two rotor webs (6a, 6b, 6c) are shaped such that they form a connection to the bulge (9), which protrudes obliquely from the sheet metal plane (8).

3. The method according to claim 2, It is characterized in that The ridge (9) is connected to the sheet metal plane (8) via three rotor webs (6a, 6b, 6c), wherein the ridge (9) forms a plane parallel to the sheet metal plane (8).

4. The method according to claim 3, It is characterized by: A rotor web (6a) extends in the radial direction (10) of the sheet metal part (1), while two rotor webs (6b, 6c) are arranged in the outer circumferential region.

5. The method according to claim 1, It is characterized in that Two partial annular channels (12) are provided having different radii.

6. The method according to claim 1 or 2, It is characterized in that The sheet metal part (1) is compressed during or after forming.

7. The method according to claim 1 or 2, It is characterized by: The sheet metal part (1) is compressed counter to a radial direction (10) during or after forming.

8. A sheet metal part (1) manufactured according to the method of any one of claims 1 to 7.

9. A rotor (3) of an electric motor (4), comprising a plurality of sheet metal parts (1) according to claim 8 stacked on top of one another and connected to one another, wherein magnets or wires are arranged in the recesses (5).

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