Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
  • H02K15/02—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D28/00—Shaping by press-cutting; Perforating
  • B21D28/02—Punching blanks or articles with or without obtaining scrap; Notching
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D28/00—Shaping by press-cutting; Perforating
  • B21D28/02—Punching blanks or articles with or without obtaining scrap; Notching
  • B21D28/22—Notching the peripheries of circular blanks, e.g. laminations for dynamo-electric machines

Definitions

• the present disclosure relates to a method for manufacturing a lamina for a stack of such lamina, i.e. a laminate, such as applied as the core of a rotor or a stator of an electric machine, e.g. an electric motor.
• the known lamina is typically produced from electric steel and is either disc shaped (rotor core) or ring shaped (stator core) with a thickness that is small relative to its diameter.
• a relatively slender crosspiece or bridge can be formed between two larger parts of the lamina, such as the pole teeth thereof.
• the crosspiece it becomes possible to form the crosspiece not only relatively narrow in the principal plane of the lamina, but also relatively thin in a direction perpendicular to such principal plane, i.e. in thickness direction.
• Such slender crosspieces favourably reduce unwanted magnetic leakage flux and/or parasitic magnetic losses.
• the crosspieces are formed by plastic deformation their magnetic permeability is favourably reduced further.
• the known lamina is typically cut and shaped out of electric steel basic material in a blanking process, such that the crosspieces are formed in thickness direction by pressing and in width direction by blanking.
• the blanking process is, as such, well-known and is broadly applied in the manufacturing of metal parts.
• the known blanking process and device at least the 2D contour of the lamina is cut out of a sheet or strip of basic material by pressing a correspondingly shaped blanking punch through the basic material that, at the same time, is firmly and held in place by and between a blanking die and a blank holder of the blanking device that each define a respective cavity shaped to accommodate and guide the blanking punch.
• the cut edge thereof can generally be more accurately formed than without exerting such pressure, i.e. without applying the counter punch. Additionally, by exerting such pressure the lamina can, to a certain extent, be shaped in 3D by the plastic deformation of the basic material. This particular arrangement of the blanking process is known as fine-blanking.
• the above known manufacturing method of the lamina in particular the step of forming the localized depression therein, requires the application of an unfavourably high (pressing) force and, moreover, may easily result in a small, but notional shortcoming in the resulting shape of the lamina.
• the basic material is locally (i.e. at the location of the crosspiece) displaced to (locally) reduce the thickness thereof.
• This displaced basic material will end up in another location on the lamina, where it increases the thickness thereof.
• an increasingly higher pressing force is disadvantageously required.
• any remaining area of increased thickness is principally undesirable and can be detrimental to the application of the lamina.
• any such systematic flatness deviation accumulates over the height of the stack.
• the crosspiece was already cut to width before being pressed, its width will inadvertently increase again by the said displacement of the basic material when being pressed to reduce its thickness.
• the cross sectional area of the cross piece will not be reduced by the said pressing thereof, at least not to the desired extent. Also, it becomes difficult to accurately control the (cross sectional) shape and dimensions of the crosspiece.
• each lamina is formed out of the basic material in at least three steps by:
• the volume of basic material that is displaced to reduce the thickness of the crosspieces relative to the (nominal) thickness of the basic material can flow more easily, in particular can flow at least partly into the free space provided by the hole or holes. Therefore, the said required pressing force is reduced and/or the dimensional accuracy of the lamina is improved.
• the piercing punches applied in the said first step and/or the press-shaping tools applied in the said second step are provided with an essentially cylindrical shape with an essentially circular cross-section.
• This design of the piercing punches and/or press-shaping tools is favourable, because it provides a relatively high strength and wear resistance at relatively low cost.
• the diameter of the cylindrical press-shaping tools corresponds to and defines a length of the crosspiece.
• the crosspiece is finally formed with either the known blanking or the known fine-blanking process with a front side of the blanking punch and/or of the counter punch applied therein, which front side engages a respective principal plane of the basic material, being provided with raised sections corresponding in location and size with the crosspieces.
• novel lamina manufacturing method i.e. preferably one of the press-shaping tools applied in the second step also serves as the blanking punch of the blanking device in the third step and the other press-shaping tool applied in the second step also serves as the counter punch of the blanking device in the third step.
• the said second and third steps are carried out in short succession or even, at least partly, simultaneously, meaning that the pressure applied in the second step to compress the basic material need to necessarily be removed in the third step, but can be maintained therein.
• Figure 1 schematically depicts an electrical machine in cross section
• Figure 2 is a schematic perspective view of a laminated stator core of the electric machine of figure 1 including a close-up of a detail of a single lamina thereof with a thin section or crosspiece;
• FIGs 3A to 3C schematically illustrate a novel manufacturing method of the lamina of figure 2, in particular of the crosspiece thereof.
• an electrical machine 10 is schematically shown in a simplified cross-section thereof.
• the electric machine 10 may be an electric motor (commutator motor, electronically commutated DC motor, AC motor, etc.), a generator, or the like. If the electric machine 10 is used as a motor, it be part of a larger drive device, for example for a window regulator in a motor vehicle.
• the electric machine 10 of figure 1 comprises a rotor 12 which is arranged on a shaft 14. Furthermore, the electric machine 10 comprises a stator 16, which is arranged around the rotor 12 and in turn is mounted in a container ring or yoke 18.
• the stator 16 is constructed substantially annular and has circumferentially arranged, outwardly facing pole teeth 20.
• the stator 16 is constructed substantially annular and has circumferentially arranged, outwardly facing pole teeth 20.
• copper wire windings 22 are arranged in a known manner.
• Successive pole teeth 20 are connected to one another via ring- segment-shaped web parts 24 of the stator 16.
• the web parts 24 are shown to taper starting from the pole teeth 20, until they are narrowest essentially halfway between two successive pole teeth 20.
• stator 16 In figure 2, it is shown in a perspective view of the stator 16 that it is composed of individual stator laminas 28 stacked on top of each other to form a laminated stator core 26.
• the stator laminas 28 are connected together in a known manner.
• the rotor 12 of the electric machine is typically laminated (not shown).
• Figure 2 also includes a close-up a single stator lamina 28 showing only a section thereof including the web part 24.
• the web part 24 is shown to include a thin middle section 30, i.e. crosspiece 30, of small thickness“d”, at least relative to a nominal thickness“D” of the lamina 28 between its two principal planes 32, 34.
• the crosspiece 30 is preferably formed by locally compressing the material of the lamina 28, either before the lamina 28 is cut from a sheet of basic material, in particular electric steel, or thereafter.
• the crosspieces are formed by plastic deformation, rather than by grinding or cutting, the magnetic permeability thereof is favourably reduced further.
• the accuracy of the overall shape lamina 28 appears to be detrimentally affected by such process step of forming the crosspieces 30 by the local compression of the lamina 28.
• the flatness of either one or both of the principal planes 32, 34 of the lamina 28 is less than without such local compression and/or a width of crosspieces 30 is increased, or at least is less accurately defined, than without such local compression.
• the present disclosure proposes a novel manufacturing method including at least the three steps that are schematically illustrated in the figures 3A, 3B and 3C successively.
• Each such figure 3A, 3B, 3C shows the basic material 50 in a top elevation as well as in a cross-section A-A thereof, while being processed in a respective manufacturing method step.
• a pair of holes is punched into the basic material 50 on either side of each respective crosspiece 30’ of the lamina 28’ to be formed, by means of respective pairs of piercing punches 60 that locally remove portions 51 of the basic material 50.
• the piercing punches 60 are shaped cylindrical.
• the circumferences of the punched holes preferably touch on the radial inner and on the radial outer contours of the lamina 28’ to be formed.
• some basic material 50 e.g. less than 50% of the width, i.e. a transverse dimension, of the crosspieces 30’ to be formed, may also be left there between.
• the crosspieces 30’ to be formed between each of said pairs of holes 31 is compressed between two press-shaping tools 70, 71 that are provided on either side of the basic material 50 and that are thereto forced together.
• the thickness d of the basic material 50 at crosspieces 30’ to be formed is reduced by plastic deformation and the displacement of material into the free space provided by the holes 31 to either side thereof.
• all of the crosspieces 30’ to be formed are compressed simultaneously in this second method step.
• width direction of the of the crosspiece 30’ to be formed exceeds a width thereof, e.g. by more than 50% of such width, whereby the flatness of the basic material 50 at the location of such crosspiece 30’ to be formed is favourably maintained or even improved.
• at least one press-shaping tool 70 is preferably shaped cylindrical.
• the lamina 28 including the crosspieces 30 thereof is finally formed in a known manner, in particular in a blanking process.
• a blanking punch 80 in particular a front side thereof, with an outer contour essentially corresponding to the contour of the lamina 28 is pushed against and cuts through the basic material 50 that is kept in place relative to the blanking punch 80 by a blanking die 81 with an inner contour essentially corresponding of the contour of the lamina 28.
• a blanking holder (not shown) is applied in the blanking process as well, on the opposite side of the basic material 50 from the blanking die 81 , to clamp and hold the basic material 50 in place between them, while the planking punch 80 cuts through it.
• a counter punch (not shown) may be applied, in the blanking process, on the opposite side of the basic material 50 from the blanking punch 80, to clamp and hold the lamina 28’ to be formed in place between them, while the planking punch 80 cuts through the basic material 50.
• the blanking punch 80 and the counter punch can also serve as the said two press-shaping tools 70, 71 in the second method step. In either case, i.e.
• the front side of the blanking punch 80, and/or possibly the counter punch in case of fine- blanking is preferably provided with raised sections 82 corresponding in location and size with the crosspieces 30. By these raised section 82, it can be prevented that the thin and thus relatively weak crosspieces 30 bend in the blanking process.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Power Engineering (AREA)
• Manufacture Of Motors, Generators (AREA)

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• 2018
  • 2018-12-20 WO PCT/EP2018/025331 patent/WO2019120626A1/en unknown
  • 2018-12-20 EP EP18833840.4A patent/EP3727717A1/de active Pending

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