JP2018007518A - Metal mold for manufacturing rotor core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relieve stress concentration of a magnetic material thin plate when plastic processing for reinforcing a bridge part is performed with a metal mold for manufacturing a rotor core.SOLUTION: A metal mold for manufacturing a rotor core comprises: a die part used for the rotor core to support a back face of a magnetic material thin plate having a plurality of holes; and a punch part having a crushing punch extending thin and long corresponding to a bridge part extending thin and log between adjacent holes of the magnetic material thin plate supported by the die part to crush the bridge part from an upper face side and make it plastically flow. The crushing punch has an arcuate slope part which gradually decreases width toward a tip side extending thin and long and also gradually decreasing in height, a surface of the crushing punch having a coefficient of friction when the magnetic material plastically flows in a first direction from the bridge part to the holes smaller than that when the magnetic material plastically flows in a second direction perpendicular to the first direction.SELECTED DRAWING: Figure 6

Description

  The present disclosure relates to a rotating electrical machine rotor manufacturing apparatus, and more particularly, to a mold for manufacturing a rotor core.

  The rotor core of an interior permanent magnet rotating electrical machine forms a laminate in which a plurality of core pieces each having a magnet insertion hole for arranging a permanent magnet are laminated, and a permanent magnet is placed in each magnet insertion hole. Manufactured by inserting and embedding. In the case of a permanent magnet with a rectangular cross section, the magnet insertion hole is a rectangular hole larger than the permanent magnet, but the both ends of the rectangular hole are extended to narrow the magnetic path between adjacent magnet insertion holes to form a bridge portion Then, the leakage of magnetic flux between adjacent permanent magnets is suppressed. Since the bridge portion is a narrow portion of the magnetic material, mechanical strength may not be sufficient, and consideration must be given so that the bridge portion is not deformed by centrifugal force or the like when the rotor rotates.

  Patent Document 1 discloses a method of manufacturing a core piece of a rotor of a rotating electrical machine by performing press hardening or the like for providing a step at a portion where stress concentration occurs in a bridge portion to improve the strength.

  In Patent Document 2, as a method for manufacturing a core piece of a rotor of a rotating electrical machine, it is disclosed that an inclined portion in which a plate thickness is continuously changed from an end portion of a magnet insertion hole is provided in a bridge portion. Here, in order to prevent the surplus thickness from moving to another part and increasing the thickness of the part when the sheet thickness is continuously reduced, an escape hole is provided in the vicinity of the bridge part. Discloses a procedure for forming an inclined portion by coining and then punching out a magnet insertion hole.

Japanese Patent Laying-Open No. 2005-094940 JP 2005-185081 A

  When plastic working is performed using a mold to strengthen the bridge between adjacent holes in the magnetic thin plate used for the rotor core, the magnetic thin plate is subjected to plastic working due to the retention of plastic flow of the magnetic material. Stress concentration is likely to occur at the boundary between the bent portion and the portion not subjected to plastic working. When stress concentration occurs, the mechanical strength of the portion decreases. Therefore, there is a demand for a mold for manufacturing a rotor core that can alleviate stress concentration in a magnetic thin plate when plastic working for strengthening a bridge portion is performed.

  A rotor core manufacturing mold according to the present disclosure is elongated between a die portion that is used for a rotor core and supports a back surface of a magnetic thin plate having a plurality of holes, and an adjacent hole of the magnetic thin plate supported by the die portion. And a punch portion having a crushing punch that is elongated corresponding to the extending bridge portion and plastically flows by crushing the bridge portion from the upper surface side, and the crushing punch gradually narrows in width as it goes to the elongated end side. And the surface of the crushing punch has a friction coefficient when the magnetic material plastically flows in the first direction from the bridge part to the hole in the first direction. It is smaller than the friction coefficient when the magnetic material plastically flows in the second perpendicular direction.

  According to the rotor core manufacturing die according to the present disclosure, the crushing punch has the arc-shaped inclined portion on the tip side, and the friction coefficient is increased or decreased depending on the direction of the surface of the crushing punch. Magnetic material tends to plastically flow in one direction. Thereby, the stay of the plastic material in the plastic flow is suppressed, and the stress concentration in the magnetic thin plate can be alleviated.

It is a figure which shows the metal mold | die for manufacture of the rotor core which concerns on this Embodiment. FIG. 1A is an arrangement view of a die portion, a punch portion, and a magnetic thin plate as a workpiece of a rotor core manufacturing die, and FIG. 1B is a view showing a state where the punch portion is opened from the rotor core manufacturing die. It is a figure which shows the crushing punch arrange | positioned on the upper surface of a punch part. It is a figure which shows the relationship between the several hole in the magnetic body thin plate with which the metal mold | die for rotor core manufacture which concerns on this Embodiment is applied, and the crushing punch of a punch part. FIG. 2A is a top view of a magnetic thin plate in which holes are formed, and FIG. 2B is an enlarged view of one magnetic pole of FIG. (C) is a top view of a punch part, (d) is an enlarged view for one magnetic pole of (c). It is a perspective view of the crushing punch shown in FIG.2 (d). It is an enlarged view of the crushing punch of FIG. It is a perspective view which shows the work hardening surface when a bridge | bridging part reinforcement | strengthening process is performed to the bridge | bridging part using the metal mold | die for rotor core manufacture which concerns on this Embodiment. It is a figure which shows the uneven | corrugated groove | channel provided on the surface of the crushing punch of the metal mold | die for rotor core manufacture which concerns on this Embodiment. It is a figure which shows the processing tool and processing direction which form the uneven | corrugated groove | channel of FIG. It is a figure which shows the work hardening surface of a bridge part when the crushing punch of FIG. 6 is used. FIG. 7 is a cross-sectional view taken along the line A-A ′ in a state where the crushing punch of FIG. 4 is pressed against the work hardening surface of FIG. 6. (A) is a figure which shows the B section in which the discontinuous part has arisen in the external shape outline of a bridge | bridging part in the boundary of the work hardening surface of FIG. (B) is a figure which shows after processing the discontinuous part of (a) smoothly. It is a figure which shows the example of the other shape of a crushing punch. FIG. 12A is a diagram showing the relationship between holes in the magnetic thin plate and crushing punches having other shapes, and FIG. 12B is a sectional view taken along line BB in FIG. (C) is the enlarged view of the C section in (b). It is a figure which shows the example of the crushing punch of a prior art. FIG. 13 is a stress distribution diagram when the bridge portion strengthening process is performed on the bridge portion using the crushing punch of FIG. 12. It is a figure which shows the stress distribution in a bridge | bridging part cross section using sectional drawing along the DD line | wire of FIG. FIG. 15A is a diagram showing the degree of stress concentration in the case of a large notch radius, and FIG. 15B is a diagram showing the degree of stress concentration in the case of a small notch radius. FIG. It is a figure which shows the stress distribution in the bridge | bridging part cross section when a bridge | bridging part reinforcement | strengthening process is performed to the bridge | bridging part using the crushing punch of the metal mold | die for rotor core manufacturing concerning this Embodiment using FIG.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. The shapes, dimensions, angles, materials, the number of holes, the number of magnetic poles and the like described below are examples for explanation, and can be appropriately changed depending on the specifications of the rotor of the rotating electrical machine. In the following description, the same elements are denoted by the same reference symbols in all the drawings, and redundant description is omitted.

  FIG. 1 is a view showing a mold 40 for manufacturing a rotor core. Hereinafter, the rotor mold manufacturing mold 40 is referred to as a mold 40 unless otherwise specified. The mold 40 is a part of a rotor core manufacturing apparatus. The rotor core is formed by laminating a predetermined number of core pieces 18 (see FIG. 2A) having a plurality of magnet insertion holes forming magnetic poles. The rotor core manufacturing apparatus includes a core piece manufacturing apparatus and a stacking apparatus. The mold 40 is used in a core piece manufacturing apparatus.

  The core piece manufacturing apparatus is an apparatus for forming the core piece 18 from the long sheet-like magnetic thin plate 10, and a progressive press molding apparatus having a plurality of molding stations is used. Hereinafter, unless otherwise specified, the sheet-like magnetic thin plate 10 is referred to as a magnetic thin plate 10.

  The magnetic thin plate 10 has a sheet width sufficiently larger than the outer diameter of the core piece 18 and has a predetermined plate thickness t0. A magnetic steel sheet is used as the material. Both surfaces of the magnetic thin plate 10 are subjected to insulation treatment such as insulation coating. By this insulation coating, the laminated core pieces 18 are electrically insulated from each other in the rotor core used in the rotating electrical machine rotor, and the eddy current that can be generated by the externally varying magnetic field is divided into small loops. Loss can be suppressed.

  Although not shown in the drawing, the magnetic thin plate 10 is provided with a plurality of feed holes at a predetermined pitch along the longitudinal direction, and the magnetic thin plate 10 is sequentially fed in the feed direction using the feed holes. The predetermined molding is sequentially performed. In FIG. 1, the direction from the near side of the paper to the other side is the feeding direction of the magnetic thin plate 10. Each forming station includes a punching station, a bridge strengthening station, and an outline punching station in the feeding order. The core piece 18 is punched from the magnetic thin plate 10 at the outer shape punching station, and the plurality of punched core pieces 18 are then laminated in a laminating apparatus to become a rotor core.

  In the above, three stations have been described. However, this is merely an example, and additional processing stations such as finish punching may be separately provided according to the specifications of the core piece 18. In the above description, the progressive press forming apparatus is described as the core piece manufacturing apparatus, but instead of this, a hole punching press apparatus, a bridge portion strengthening press apparatus, an outer shape press apparatus, and the like may be individually provided.

  The mold 40 is used at the bridge strengthening station. Since the front of the bridge portion strengthening station is a hole punching station, the magnetic thin plate 10 is conveyed to the bridge portion strengthening station in a state where a plurality of holes are punched out.

  FIG. 1 is a view showing a mold 40 in the bridge portion strengthening station. The magnetic thin plate 10 is not a component of the mold 40, but is a workpiece to be subjected to the bridge portion strengthening process. The mold 40 includes a die portion 42 that supports the back surface of the magnetic thin plate 10 and a punch portion 44 that faces the upper surface of the magnetic thin plate 10. FIG. 1A is a diagram showing that the die part 42 and the punch part 44 are arranged with the magnetic thin plate 10 interposed therebetween.

  The front surface of the magnetic thin plate 10 is the upper surface ST, and the surface opposite to the upper surface ST is the rear surface SB of the magnetic thin plate 10. In the die portion 42, the surface facing the back surface SB of the magnetic thin plate 10 is defined as the upper surface DT of the die portion 42, and the surface opposite to the upper surface DT is defined as the lower surface DB of the die portion 42. In the punch portion 44, a surface facing the upper surface ST of the magnetic thin plate 10 is defined as an upper surface PT of the punch portion 44, and a surface opposite to the upper surface PT is defined as a lower surface PB of the punch portion 44. In FIG. 1A, from the upper side to the lower side in the drawing, (PB of punch portion 44) − (PT of punch portion) − (ST of magnetic thin plate 10) − (SB of magnetic thin plate 10). -(DT of the die part 42)-(DB of the die part 42) are arranged in this order.

  FIG. 1B is a diagram showing a state in which the punch portion 44 is opened in the arrow direction with respect to the die portion 42 and the upper surface PT of the punch portion 44 is directed upward. On the upper surface PT of the punch portion 44, crushing punches 50 and 51 for reinforcing the bridge portion are arranged.

  The bridge portion strengthening process is a process for improving the mechanical strength of the bridge portion in which the magnetic path between adjacent holes in the magnetic thin plate 10 is narrowed. Specifically, the back surface SB of the magnetic thin plate 10 is supported by the upper surface DT of the die portion 42, and the crushing punches 50 and 51 on the upper surface PT of the punch portion 44 face the upper surface ST of the bridge portion of the magnetic thin plate 10. . Then, the punch portion 44 is lowered with respect to the die portion 42, and the crushing punches 50 and 51 are used to crush a predetermined crushing shape with a predetermined crushing pressure in the thickness direction of the magnetic thin plate 10 from the upper surface ST side of the bridge portion. Crush it so that The portion that is crushed in the bridge portion undergoes work hardening by plastic working, and the mechanical strength is improved. As a result, the bridge portion is strengthened.

  In order to cause work hardening, when the crushing punches 50 and 51 are pressed with a predetermined crushing pressure in the thickness direction of the magnetic thin plate 10, the magnetic material is plastically deformed and fluidized in the pressing portion and thinned in the thickness direction. However, the magnetic material of that part moves to another part. If the periphery of the pressing portion is surrounded by the magnetic material, the fluidity of the magnetic material may be reduced, and the magnetic thin plate 10 may be warped. When the magnetic thin plate 10 is warped, the core piece 18 punched thereafter is warped, the space factor of the core piece 18 in the rotor core is lowered, and the lamination process is hindered.

  In the present embodiment, when a plurality of holes per magnetic pole are collectively referred to as a hole assembly 12, the magnetic thin plate 10 that has already been subjected to the punching process and has a plurality of hole assemblies 12 corresponding to the number of magnetic poles. Bridge portion reinforcement processing is performed. That is, since both sides of the bridge portion that is the pressing portion of the crushing punches 50 and 51 are holes, the magnetic material plastically deformed in the pressing portion tends to flow toward the holes. By improving the fluidity of the magnetic material, the warpage of the magnetic thin plate 10 is suppressed, the space factor of the core piece 18 in the rotor core is prevented from being lowered, and the laminating process is not hindered.

  FIG. 2 is a view showing a state where the punch portion 44 is opened before the bridge portion strengthening process is performed, although the magnetic thin plate 10 has been transported to the bridge portion strengthening station. 2A and 2B are views showing the upper surface ST of the magnetic thin plate 10, and FIGS. 2C and 2D are views showing the upper surface PT of the punch portion 44. FIG.

  FIG. 2A is a view showing a state in which a plurality of hole assemblies 12 have already been subjected to the punching process in the magnetic thin plate 10. The plurality of hole assemblies 12 are arranged in an annular shape, and the number of arrangements is the same as the number of magnetic poles of the rotor. In the example of FIG. 2 (a), the number of arrangements of the plurality of hole assemblies 12 is 8, and the number of magnetic poles of the rotor is 8. When the bridge portion strengthening process is performed on the plurality of hole assemblies 12, an outline removing process is performed thereafter. In FIG. 2A, the center hole 14 and the outer shape punched hole 16 punched in the outer shape removing process are indicated by a two-dot chain line. A core piece 18 is punched from the magnetic thin plate 10 by outer shape removal. The center hole 14 may be formed by a hole removing process for forming a plurality of hole assemblies 12 without using the outline removing process.

  FIG. 2B is an enlarged view of one magnetic pole of FIG. The plurality of hole assemblies 12 for one magnetic pole include holes 20, 21, 22, 24 and two small holes that are not labeled. The holes 20, 21, and 24 are magnet insertion holes into which permanent magnets that form the magnetic poles of the rotor are inserted. The holes 22 and the two small holes are provided to narrow the magnetic path and reduce the weight. It is. The holes 20, 21 and the two small holes without reference numerals are arranged symmetrically with respect to the magnetic pole center line 26, and the holes 22, 24 have a shape symmetrical with respect to the magnetic pole center line 26.

  The bridge portion 30 is a narrow portion of the magnetic passage extending elongated between the hole 22 and the hole 20, and the bridge portion 31 is a narrow portion of the magnetic passage extending elongated between the hole 22 and the hole 21. The bridge portions 30 and 31 are also arranged symmetrically with respect to the center line 26 of the magnetic pole. Since there are two bridge portions 30 and 31 per magnetic pole, there are eight sets of bridge portions 30 and 31 per core piece 18. The length L0 in the longitudinal direction of each of the bridge portions 30 and 31 is the length of the region where the magnetic path is narrower than the other portions, and is longer than the length of the region where the width of the bridge portions 30 and 31 is constant W0. long.

  2C and 2D are views showing the upper surface PT of the punch portion 44 facing the upper surface ST of the magnetic thin plate 10. (C) is a top view of the punch portion 44, and (d) is an enlarged view of one magnetic pole. In these, the arrangement positions of the hole assembly 12, the center hole 14, and the outer shape punching hole 16 are indicated by two-dot chain lines. The crushing punches 50 and 51 provided on the upper surface PT of the punch portion 44 are disposed at positions corresponding to the bridge portions 30 and 31 of the magnetic thin plate 10 and extend elongated corresponding to the elongated bridge portions 30 and 31. Since one set of crushing punches 50 and 51 is provided per magnetic pole, eight sets of crushing punches 50 and 51 are provided in the entire punch portion 44 per one core piece 18.

  The length L1 in the longitudinal direction of each crushing punch 50, 51 is shorter than the length L0 in the longitudinal direction of the bridge portions 30, 31 (the length of the region where the width dimension of the bridge portions 30, 31 is constant W0). ) Is set in consideration of (positioning accuracy between the mold 40 and the magnetic thin plate 10). The width W1 of the crushing punches 50 and 51 preferably has a margin of hp on both sides of each width of the crushing punches 50 and 51, with the height hp based on the PT of the crushing punches 50 and 51 being h1. Therefore, the width W1 of the crushing punches 50 and 51 is preferably set in a range of W0 ≦ W1 ≦ (W0 + 2h1).

  FIG. 2D shows the direction of the height hp of the crushing punches 50 and 51 as well as the radial direction and the circumferential direction in the punch portion 44. The radial direction is a direction along the center line 26 of the magnetic pole, and a direction toward the outer peripheral side is a positive direction (+), and a direction toward the inner peripheral side is a negative direction (−). The circumferential direction is the circumferential direction of the annular core piece 18, and in the upper surface PT of the punch portion 44, the clockwise direction is the positive direction (+) and the counterclockwise direction is the negative direction (−). In FIG. 2D, the right direction of the center line 26 of the magnetic pole is the positive direction (+) in the circumferential direction, and the left direction is the negative direction (−) in the circumferential direction. As for the direction of the height hp of the crushing punches 50 and 51, the upper side of the upper surface PT is defined as the positive direction (+) with reference to the upper surface PT of the punch portion 44. The upper surface PT of the punch portion 44 has a height hp = 0, and the crushing punches 50 and 51 protrude at a height hp = h1 from the upper surface PT. Therefore, the height hp of the crushing punches 50 and 51 is hp = h1> 0. It is.

  Returning to FIG. 2 (b), the direction of the crushing depth hs in the bridge portions 30 and 31 is shown together with the radial direction and the circumferential direction in the magnetic thin plate 10. The radial direction is a direction along the center line 26 of the magnetic pole, and a direction toward the outer peripheral side is a positive direction (+), and a direction toward the inner peripheral side is a negative direction (−). This is the same as the radial direction of the punch portion 44.

  The circumferential direction of the magnetic thin plate 10 is the circumferential direction of the annular core piece 18, but the upper surface ST of the magnetic thin plate 10 faces the upper surface PT of the punch portion 44. When the direction is a reference, the circumferential direction of the magnetic thin plate 10 is reversed. That is, the clockwise direction on the upper surface ST of the magnetic thin plate 10 is the negative direction (−), and the counterclockwise direction is the positive direction (+). In FIG. 2B, the left direction of the center line 26 of the magnetic pole is the positive direction (+) in the circumferential direction, and the right direction is the negative direction (−) in the circumferential direction. Due to this relationship, the bridge portion 30 on the left side of the magnetic pole center line 26 on the upper surface ST of the magnetic thin plate 10 corresponds to the crushing punch on the right side of the magnetic pole center line 26 on the upper surface PT of the punch portion 44. 50. Similarly, the crushing punch 51 located on the left side of the magnetic pole center line 26 on the upper surface PT of the punch portion 44 corresponds to the bridge portion 31 on the right side of the magnetic pole center line 26 on the upper surface ST of the magnetic thin plate 10. It becomes.

  In the magnetic thin plate 10, the direction of the crushing depth hs of the bridge portions 30 and 31 is a direction in which the plate thickness of the magnetic thin plate 10 is reduced. Therefore, the direction from the upper surface ST of the magnetic thin plate 10 toward the back surface SB is normal. Direction (+). The crushing depth hs of the bridge portions 30 and 31 is the same as the height hp of the crushing punches 50 and 51. The crushing depth hs of the upper surface ST of the magnetic thin plate 10 is 0, and the crushing depth hs of the bridge portions 30 and 31 is hs = hp> 0. hs> 0 is a direction in which the thickness t0 of the magnetic thin plate 10 is decreased.

  As shown in FIG. 2, since the plurality of hole assemblies 12 and the bridge portions 30 and 31 are axisymmetric with respect to the magnetic pole center line 26, the crushing punches 50 and 51 are also symmetrical with respect to the magnetic pole center line 26. Be placed. Since the crushing punches 50 and 51 have the same structure, the crushing punch 50 corresponding to the bridge portion 30 will be described below.

  FIG. 3 is a perspective view of the crushing punch 50. The crushing punch 50 includes two three-dimensionally shaped punch surfaces 52 </ b> P and 54 </ b> P that are arranged symmetrically with respect to the punch center line 32 </ b> P extending along the radial direction of the crushing punch 50 and project from the upper surface PT of the punch portion 44. The punch surface 52P is provided corresponding to the portion of the bridge portion 30 on the hole 20 side, and the punch surface 54P is provided corresponding to the portion of the bridge portion 30 on the hole 22 side. The punch center line 32P is disposed at a position corresponding to the bridge center line 32S (see FIG. 5) extending along the radial direction of the bridge portion 30. A flat surface 53P sandwiched between the punch surface 52P and the punch surface 54P and extending along the punch center line 32P is a part of the upper surface PT of the punch portion 44.

  The punch surfaces 52P and 54P have a flat stepped portion 56P that extends elongated along the radial direction, and arcuate inclined portions 58P at both end portions of the flat stepped portion 56P. The arcuate inclined portion 58P has a shape in which the width dimension gradually narrows and the height dimension gradually decreases as it goes toward the elongated tip end. The arcuate inclined portions 58P on both sides are symmetrical with respect to the flat stepped portion 56P. Below, about the punch surfaces 52P and 54P, the half part of the negative direction (-) side is described among the full length L1 along a radial direction.

  FIG. 4 is an enlarged view of a half portion on the negative direction (−) side in the radial direction of the full length L1 along the radial direction with respect to the crushing punch 50 in FIG. 3. The crushing punch 50 includes a flat step portion 56P on the positive direction (+) side along the radial direction and an arcuate inclined portion 58P on the negative direction (−) side in the radial direction with respect to the flat step portion 56P. Since the punch surfaces 52P and 54P constituting the crushing punch 50 are symmetrical with respect to the punch center line 32P, the punch surface 52P will be described below. Constituent elements corresponding to each of the punch surface 52P and the punch surface 54P are denoted by the same reference numerals, and redundant description is omitted.

  The flat stepped portion 56P on the punch surface 52P has a stepped wall surface 60P rising from the upper surface PT, a flat surface 62P corresponding to the ceiling surface of the top of the stepped wall surface 60P, and a lower surface inclined from the flat surface 62P toward the punch center line 32P. A center line side inclined surface 64P reaching PT is included. The height hp of the flat surface 62P is hp = h1> 0.

  Q1P, Q2P, and Q3P are shown as boundary points between the flat step portion 56P and the arc-shaped inclined portion 58P on the punch surface 52P. Q1P and Q2P have the same radial position at a point on the flat surface 62P, and the height hp from the upper surface PT is hp = h1. Q3P is a point on the upper surface PT and has the same radial position as Q1P and Q2P, and is lowered from Q2P along the centerline-side inclined surface 64P and reaches the upper surface PT.

  The arcuate inclined portion 58P is an arcuate inclined surface connecting the tip point Q4P on the negative (−) side in the radial direction and Q1P, Q2P, and Q3P. Q4P is a point on the upper surface PT, the position in the circumferential direction is the same as that of Q1P, is a point inclined downward from Q1P and reaches the upper surface PT.

  The arc-shaped inclined portion 58P includes a step wall surface 66P, an arc-shaped curved surface 68P, and an arc-shaped curved surface 70P. The step wall surface 66P includes Q1P and Q4P, and is a wall surface that rises from the upper surface PT of the punch portion 44. The arcuate curved surface 68P is a curved surface including Q1P, Q2P, and Q4P. The arcuate curved surface 70P is a curved surface including Q2P, Q3P, and Q4P.

  The arcuate curved surface 70P is an inclined curved surface that is inclined downward from the arcuate curved surface 68P at an inclination angle θ1 along the circumferential direction and heads toward the upper surface PT. A roundness of radius R1 is provided at the boundary between the arcuate curved surface 70P and the arcuate curved surface 68P. Thereby, the arcuate curved surface 68P and the arcuate curved surface 70P are smoothly connected.

  The arcuate curved surface 68P and the arcuate curved surface 70P are on the negative direction (−) side along the radial direction of the flat stepped portion 56P, and the height hp becomes hp = h1 as it goes to Q4P on the distal end side along the radial direction. To hp = 0. Further, the arcuate curved surface 68P and the arcuate curved surface 70P are curved surfaces whose width dimension gradually and gradually changes from the position of Q2P, Q3P to the position of Q4P along the circumferential direction as it goes to the tip side along the radial direction. is there. Thus, the arc-shaped curved surface 68P and the arc-shaped curved surface 70P are not stepped wall surfaces, but gradually change in height gradually toward the tip side along the radial direction, and the width dimension gradually increases along the circumferential direction. The curved surface is narrow and gradually changed.

  FIG. 5 shows a three-dimensional shape of the bridge portion 30 that is crushed when the crushing punch 50 is pressed with a predetermined crushing pressure from the upper surface ST side of the bridge portion 30 toward the plate thickness direction of the magnetic thin plate 10. FIG. Here, the enlarged view of the half part by the side of the negative direction (-) in radial direction is shown among the full length L0 extended in radial direction about the bridge part 30 corresponding to FIG.

  The crushing depth hs of the bridge portion 30 by the crushing punch 50 is the same size as the height hp of the crushing punch 50 from the upper surface ST of the bridge portion 30 in the decreasing direction of the plate thickness. That is, the crushed three-dimensional shape of the bridge portion 30 is a shape obtained by transferring the three-dimensional shape of the crushing punch 50, and is substantially the same as the three-dimensional shape of the punch surfaces 52P and 54P only in the direction of the unevenness. It is. In the following description, the suffix “P” attached to the three-dimensional shape of the punch surfaces 52P and 54P is replaced with the suffix “S” and used as the three-dimensional shape of the bridge portion 30. For example, the flat surface 62S in the bridge portion 30 indicates a corresponding surface that is crushed by the flat surface 62P of the punch surface 52P.

  The crushing punch 50 includes two three-dimensionally protruding punch surfaces 52P and 54P arranged symmetrically with respect to the punch center line 32P. Correspondingly, the bridge portion 30 also includes two three-dimensionally recessed work hardening surfaces 52S and 54S arranged symmetrically with respect to the bridge center line 32S.

  The work hardened surfaces 52S and 54S are surfaces transferred by the crushing punch 50, but the positive direction (+) and the negative direction (-) in the circumferential direction are switched in the transfer. 4 and 5, the circumferential arrangement of the holes 20 and 22 is reversed, but the work hardened surface 52S is a surface transferred by the punch surface 52P, and the work hardened surface 54S is transferred by the punch surface 54P. It is assumed that The work hardening surface 52S is provided in a portion on the hole 20 side in the bridge portion 30, and the work hardening surface 54S is provided in a portion on the hole 22 side in the bridge portion 30. A flat surface 53S sandwiched between the work hardened surface 52S and the work hardened surface 54S and extending along the bridge center line 32S is a part of the upper surface ST of the magnetic thin plate 10.

  Since the work hardened surfaces 52S and 54S are line symmetrical with respect to the bridge center line 32S, the work hardened surface 54S to be crushed by the punch face 54P will be described below. Constituent elements corresponding to the work hardened surface 54S and the work hardened surface 52S are denoted by the same reference numerals, and redundant description is omitted.

  Since the work hardening surface 54S is provided in a portion of the bridge portion 30 on the hole 22 side, the side surface 22S of the hole 22 on the bridge portion 30 side is shown in FIG. The work hardening surface 54S includes a flat stepped portion 56S and an arcuate inclined portion 58S connected to the flat stepped portion 56S along the radial direction. The flat step portion 56S and the arc-shaped inclined portion 58S are portions where the flat step portion 56P and the arc-shaped inclined portion 58P of the punch surface 54P are transferred to the bridge portion 30, respectively.

  The width W1 of the crushing punch 50 is set in a range of W0 ≦ W1 ≦ (W0 + 2h1), where the height hp from the upper surface PT of the crushing punch 50 is h1, so that the stepped wall surface 60P described in FIG. It does not touch the part 30. Therefore, the transfer surface corresponding to the stepped wall surface 60 </ b> P of the crushing punch 50 does not appear on the hole 22 side of the bridge portion 30.

  The flat step portion 56S includes a flat surface 62S and a centerline side inclined surface 64S. The flat surface 62S is a bottom surface that is inclined from the upper surface ST of the bridge portion 30 along the bridge center line 32S and is crushed to a crushing depth hs = h1. The centerline side inclined surface 64S is a surface that is inclined downward from the upper surface ST of the bridge portion 30 extending along the bridge centerline 32S toward the flat surface 62S. The flat surface 62S and the centerline side inclined surface 64S are portions where the flat surface 62P and the centerline side inclined surface 64P of the punch surface 54P are transferred to the bridge portion 30, respectively.

  The flat surface 62S is connected to the side surface 22S of the hole 22 at the end surface opposite to the bridge center line 32S. The dimension in the height direction of the side surface 22S of the hole 22 at the end of the flat surface 62S corresponds to the magnetic material thickness of {(plate thickness t0 of the magnetic thin plate 10)-(crushing depth hs = h1)}. This magnetic body thickness is the thickness of the bridge portion after the bridge portion strengthening process is performed. The compressibility along the thickness direction of the bridge portion 30 by the bridge portion strengthening process is [{(plate thickness t0 of the magnetic thin plate 10) − (crushing depth hs = h1)} / t0] × 100 (%). is there. The magnitude of the compression rate is set based on specifications such as the width W0, the length L0, the magnetic resistance, the material, and the mechanical strength of the bridge portion 30. An example of the compression rate is in the range of about 80% to 95%. This is an illustrative example, and can be changed as appropriate based on the above specifications.

  Q1S, Q2S, and Q3S are shown as boundary points of the arc-shaped inclined portion 58S connected to the flat stepped portion 56S on the work hardening surface 54S, and Q4S is used as the tip point on the negative (−) side in the radial direction of the arc-shaped inclined portion 58S. Indicates. Q1S, Q2S, Q3S, and Q4S are points where Q1P, Q2P, Q3P, and Q4P on the punch surface 54P are transferred to the bridge portion 30, respectively.

  Q1S and Q2S have the same radial position at the point on the flat surface 62S, and the crushing depth hs from the upper surface ST is also hs = h1> 0. Q3S is a point on the upper surface ST, has the same radial position as Q1S and Q2S, is raised from Q2S along the centerline-side inclined surface 64S, and reaches the upper surface ST.

  The arcuate inclined portion 58S is an arcuate inclined surface connecting the tip point Q4S on the negative (−) side in the radial direction and Q1S, Q2S, Q3S. Q4S is a point on the upper surface ST, the position in the circumferential direction is the same as that of Q1S, is inclined up from Q1S, and reaches the upper surface ST.

  As a result, the height of the side surface 22S of the hole 22 increases from Q1S having the crushing depth hs = h1 to Q4S on the upper surface ST where the crushing depth hs = 0. In FIG. 5, the surface where the side surface 22S becomes higher and reaches the upper surface ST is indicated by a triangular surface 22S '.

  The arcuate inclined portion 58S includes an arcuate curved surface 68S and an arcuate curved surface 70S. The arcuate curved surface 68S is a curved surface including Q1S, Q2S, and Q4S. The arcuate curved surface 70S is a curved surface including Q2S, Q3S, and Q4S.

  The arcuate curved surface 70S is an inclined curved surface that is inclined from the arcuate curved surface 68S at an inclination angle θ1 along the circumferential direction toward the upper surface PT of the bridge portion 30. A roundness having a radius R1 is provided at the boundary between the arcuate curved surface 70S and the arcuate curved surface 68S. Thus, the arcuate curved surface 68S and the arcuate curved surface 70S are smoothly connected.

  Since the width W1 of the crushing punch 50 is set in a range of W0 ≦ W1 ≦ (W0 + 2h1), the stepped wall surface 66P of the crushing punch 50 described with reference to FIG. The corresponding transfer surface does not appear on the hole 22 side of the bridge portion 30. Instead, a triangular surface 22S 'appears corresponding to the inclination of the step wall surface 66P.

  The arcuate curved surface 68S and the arcuate curved surface 70S are on the negative direction (−) side along the radial direction of the flat stepped portion 56S, and the crushing depth hs becomes hs = as it goes to Q4S on the tip side along the radial direction. The curved surface gradually changes from h1 to hs = 0. Further, the arc-shaped curved surface 68S and the arc-shaped curved surface 70S are curved surfaces whose width dimension gradually and gradually changes from the position of Q2S, Q3S to the position of Q4S along the circumferential direction as it goes to the tip side along the radial direction. is there. As described above, the arcuate curved surface 68S and the arcuate curved surface 70S are not stepped wall surfaces, but gradually change in the crushing depth hs gradually toward the tip side along the radial direction, and the width dimension increases along the circumferential direction. The curved surface gradually and gradually changes.

  The bridge portion strengthening process is performed by sandwiching the bridge portion 30 between the die portion 42 and the crushing punch 50 of the punch portion 44 and pressing the crushing punch 50 against the upper surface ST of the bridge portion 30. Thereby, the magnetic material of the bridge part 30 is plastically deformed and fluidized, and flows from the bridge part 30 side toward the other direction. When the magnetic material plastically flows in the direction perpendicular to the first direction on the surface of the crushing punch 50, the friction coefficient when the magnetic material plastically flows in the first direction from the bridge portion 30 toward the holes 20 and 22. A process smaller than the friction coefficient is applied. Specifically, fine concavo-convex grooves are provided on the punch surfaces 52P and 54P of the crushing punch 50 as processing marks extending along the direction from the bridge portion 30 side toward the holes 20 and 22.

  FIG. 6 shows fine concave and convex grooves 80 </ b> P provided on the punch surfaces 52 </ b> P and 54 </ b> P of the crushing punch 50. Black arrows 82P and 84P indicating the extending direction of the concave and convex grooves 80P indicate directions from the punch center line 32P side corresponding to the bridge center line 32S toward the holes 20 and 22. The direction of the black arrow 82P in the flat step portion 56P is a direction perpendicular to the punch center line 32P. The direction of the black arrow 84P in the arc-shaped inclined portion 58P is a direction that is gradually inclined with respect to the punch center line 32P from the flat stepped portion 56P side to the tip side along the radial direction. The directions of the black arrows 82P and 84P are the first direction from the bridge portion 30 toward the holes 20 and 22, and the direction perpendicular to the directions of the black arrows 82P and 84P is the second direction.

  FIG. 7 is a diagram illustrating a method of forming the concave and convex groove 80P. Here, a processing tool 86 having an appropriate rounded end is pressed against the surfaces of the punch surfaces 52P and 54P of the crushing punch 50, and the direction parallel to the first direction, which is the direction of the black arrows 82P and 84P, is defined as the processing direction. Move.

  The concavo-convex groove 80P may be a step groove that concavo-convex perpendicularly to the surfaces of the punch surfaces 52P, 54P. preferable. Moreover, as shown in FIG. 7, it is preferable that the ridges and valleys of the unevenness have appropriate roundness. The concave / convex depth of the concave / convex groove 80P may be such that anisotropy occurs in the coefficient of friction against plastic flow of a magnetic material that is plastically deformed and fluidized under a predetermined crushing pressure. The anisotropy of the friction coefficient with respect to the plastic flow is (the friction coefficient along the first direction which is the direction of the black arrows 82P and 84P)> (along the second direction perpendicular to the directions of the black arrows 82P and 84P) Friction coefficient). The unevenness depth is the surface roughness of the punch surfaces 52P and 54P. For example, the unevenness depth may be approximately 1 μm or less. Preferably, the depth of unevenness is about 200 nm.

  In FIG. 7, the concave and convex grooves 80P continuous along the processing direction are shown. However, since it is sufficient that the friction coefficient with respect to plastic flow is anisotropic, the processing direction is the longitudinal direction and the direction perpendicular to the processing direction is short. You may provide many elongate uneven | corrugated hollows made into a direction. The method for forming the uneven groove 80P may be other than the method using the processing tool 86 shown in FIG. For example, the concave and convex grooves 80P may be formed on the punch surfaces 52P and 54P by transfer using a mother die on which concave and convex grooves are formed in advance. Alternatively, techniques such as shot peening and etching under appropriate conditions may be used.

  FIG. 8 is a view showing the bridge portion 30 formed using the crushing punch 50 of FIG. Corrugated grooves 80S are formed on the work hardened surfaces 52S and 54S of the bridge portion 30 corresponding to the concave and convex grooves 80P provided on the surfaces of the punch surfaces 52P and 54P of the crushing punch 50. The concave / convex groove 80S extends in the direction of the black arrows 82S and 84S. The direction of the black arrows 82S and 84S corresponds to the first direction which is the direction of the black arrows 82P and 84P on the punch surfaces 52P and 54P. Accordingly, the magnetic material that has been plastically deformed and fluidized under a predetermined crushing pressure on the work hardened surfaces 52S and 54S extends in the direction of the black arrows 82S and 84S, which is the first direction, to the holes 20 and 22. It is shown that it is flowing.

  FIG. 9 is a cross-sectional view showing the state of the punch surface 54P and the work hardened surface 54S that are pressed against each other in the bridge portion strengthening process. FIG. 9 is a cross section along the A-A ′ line (see FIGS. 4 and 5) parallel to the circumferential direction in the arc-shaped inclined portion 58 </ b> S. The arcuate inclined portion 58S is a tip end portion extending along the radial direction on the work hardening surface 54S, and a short side portion (FIGS. 12 to 14) in which stress concentration easily occurs on a rectangular work hardening surface of the prior art described later. This corresponds to the reference).

  As shown in FIG. 9, the work hardened surface 54S corresponds to a transfer surface of the punch surface 54P, and the upper surface of the crushing depth hs = 0 from the arcuate curved surface 68S having a crushing depth hs in the arcuate inclined portion 58S. An arcuate curved surface 70S that gradually changes at an inclination angle θ1 in the plate thickness direction toward the ST is provided. At the position where the inclination starts, it has a radius R1. As described above, in the arc-shaped inclined portion 58S, the crushing depth hs of the work hardened surface 52S gradually changes in the plate thickness direction at the inclination angle θ1. The flow direction when the magnetic material fluidizes and moves as the plate thickness gradually changes is the direction indicated by the black arrow 84S.

  As the inclination angle θ1 is smaller, the stress concentration can be reduced, but the length of the work hardened surface 52S becomes longer. When the inclination angle θ1 is large, the length of the work hardened surface 52S can be shortened, but the stress concentration becomes large. The inclination angle θ1 is determined based on this balance. As an example, the inclination angle θ1 may be in the range of about 15 degrees to 30 degrees. As for the roundness of the radius R1, the smaller the inclination angle θ1, the larger the radius. As an example, the radius R1 is about 0.2 mm. These are examples for explanation, and can be appropriately changed depending on the specifications of the mold 40.

  FIG. 10 is a diagram illustrating a boundary portion between the work hardened surface 54S that has undergone the bridge portion strengthening process and the upper surface ST that has not undergone the bridge portion strengthening process. FIG. 10A is a plan view of a portion B in FIG. The work hardened surface 54S is fluidized by plastic working due to the pressing of the punch surface 54P and flows toward the hole 22, and has an edge shape toward the hole 22 from the original outline of the bridge portion 30. Stick out. Therefore, a concave discontinuous portion 92 is generated in the outer contour line 90 of the bridge portion 30 in the B portion which is a boundary portion with the upper surface ST where the magnetic material is not fluidized.

  FIG. 10B is a diagram showing the outer contour 94 of the bridge portion 30 after the processing for smoothing the discontinuous portion 92 in FIG. As the processing for smoothing the discontinuous portion 92, after the bridge portion strengthening processing, a method of performing the finish removal for the hole aggregate 12, a polishing treatment or a crushing treatment for the discontinuous portion 92, instead of the finish removal, etc. You may go.

  In the above description, the width W1 of the crushing punch 50 is set to a range of W0 ≦ W1 ≦ (W0 + 2h1), where the height hp from the PT of the crushing punch 50 is h1, so that the width W1 is substantially the same as the width W0 of the bridge portion 30. It is. For this purpose, the crushing punch 50 has an elongated shape as shown in FIG. 6, and it is necessary to manage the dimension of the width W1. Since both sides of the bridge portion 30 are the holes 20 and 24, there is a margin for expanding the width of the crushing punch 50. FIG. 11 shows an example of a wide crushing punch 100.

  FIG. 11A is a view showing the lower surface PB of the wide crushing punch 100. The wide crushing punch 100 has two punch surfaces 102P and 104P arranged symmetrically with respect to the punch center line 32P. A two-dot chain line shown in FIG. 11A is an outline contour line of the bridge portion 30, and the bridge center line 32S is aligned with the punch center line 32P. The two punch surfaces 102P and 104P extend beyond the outline of the bridge portion 30 toward the holes 20 and 22, and the width W2 of the crushing punch 100 is wider than the width W1 of the crushing punch 50 in FIG. Except for the fact that the width W2 is wider than the width W1, the basic structure of the three-dimensional shape of the crushing punch 100 is the same as that of the crushing punch 50, and the two punch surfaces 102P and 104P have a flat step at the center along the radial direction. Part 106P and arcuate inclined parts 108P on both sides of flat stepped part 106P.

  FIG.11 (b) is sectional drawing along the BB line of (a). Here, the punch surface 104P and the die part 42 are shown. (C) is an enlarged view of part C of (b), showing the inclination of the arcuate curved surface in the arcuate inclined part 108P. Even if the crushing punch 100 of FIG. 11 is used, the bridge part reinforcement | strengthening process similar to the crushing punch 50 of FIG. 4 can be performed, and the same work hardening surfaces 52S and 54S can be obtained.

  In the above description, the radial direction of the magnetic thin plate 10, the bridge portion 30, the crushing punch 50, the work hardening surfaces 52S and 54S, the positive direction and the negative direction in the circumferential direction are described with reference to the punch portion 44. Is considered as a direction in which the radial direction extends and the circumferential direction is the width direction. Therefore, the rotor core manufacturing mold 40 according to the present embodiment includes a die portion 42 that is used for the rotor core and supports the back surface SB of the magnetic thin plate 10 having a plurality of holes. At the same time, the bridge 30 is elongated corresponding to the bridge 30 extending between the adjacent holes 20 and 22 of the magnetic thin plate 10 supported by the die 42, and the bridge 30 is crushed from the upper surface ST side to cause plastic flow. The punch part which has the punch 50 is provided. The crushing punch 50 has an arcuate inclined portion 58P in which the width dimension is gradually narrowed and the height hp is gradually lowered as it goes to the elongated end. Furthermore, the surface of the crushing punch 50 has a coefficient of friction when the magnetic material plastically flows in the first direction from the bridge portion 30 toward the holes 20 and 22, and the magnetic material is in the second direction perpendicular to the first direction. It is smaller than the friction coefficient when plastically flowing.

  The operation and effect of the above configuration will be described in more detail below with reference to FIGS. 12 to 16 as compared to an example in which the bridge portion strengthening process is performed using a conventional crushing punch.

  FIG. 12 is a perspective view of a conventional crushing punch 110. Similar to the crushing punch 50 of FIG. 4 according to the present embodiment, the crushing punch 110 of the prior art includes two punch surfaces 112P and 114P. The width W3 and the length L3 of the crushing punch 110 are substantially the same as the width W1 and the length W1 of the crushing punch 50 of FIG. 4, respectively, and the height hp from the upper surface PT of the punch portion 44 is the crushing punch of FIG. A height of 50 is the same as hp = h1. A major difference between the crushing punch 50 and the crushing punch 110 in FIG. 4 is the presence or absence of the arc-shaped inclined portion 58P. In the crushing punch 110, the two punch surfaces 112P and 114P have an elongated rectangular planar shape, and the end surface of the short side portion of the rectangle is called a pin angle 116P, and is a wall surface that rises substantially vertically from the upper surface PT of the punch portion 44. .

  FIG. 13 is a diagram illustrating a stress distribution generated in the magnetic material of the bridge portion 30 on the plan view of the bridge portion 30 when the bridge portion strengthening process is performed using the crushing punch 110. Here, a region where the stress concentration is strong is indicated by black, a region where stress concentration occurs but is relatively weak is indicated by hatching, and a region where stress concentration does not occur is indicated by neither black coating nor hatching. As shown in FIG. 13, a strong stress concentration occurs in the region of the pin angle 116 </ b> S corresponding to the pin angle 116 </ b> P of the crushing punch 110.

  FIG. 14 is a cross-sectional view of the bridge portion 30 taken along line DD in FIG. The bridge portion 30 is compressed vertically by the height hp = h1 of the crushing punch 110 from the upper surface ST at the pin angle 116S. The plate thickness at the flat bottom surface after compression is {(plate thickness t0 of magnetic thin plate 10)-(height hp = h1 of crushing punch 110)}. In FIG. 14, the degree of stress concentration generated in the magnetic material in the cross-sectional view of the bridge portion 30 is shown in four stages so that the stress concentration gradually increases from a white background to diagonal lines, double diagonal lines, and black paint. It can be seen that the stress concentration is the strongest in the vicinity of the pin angle 116S where the cross-sectional shape changes abruptly in the plate thickness direction, and that a fairly strong stress concentration spread occurs in the plate thickness direction therefrom.

  FIG. 15 is a diagram showing the degree of stress concentration depending on the size of the notch radius. FIG. 15A is a diagram showing the degree of stress concentration in the case of a large notch radius, and FIG. 15B is a diagram showing the degree of stress concentration in the case of a small notch radius. In each figure, the horizontal axis indicates the depth direction, and the vertical axis indicates the normalized stress magnitude. Comparing (a) and (b), it can be seen that a steep stress change occurs in the depth direction in the case of a small notch radius. This effect is called a notch effect, with the depth of the recess as a notch. At the pin angle 116S of the prior art crushing punch 110, the cross-sectional shape changes suddenly and the notch radius is small, so that the notch effect appears remarkably and the mechanical strength decreases at that point. Further, since the notch radius is small, the stress concentration tends to spread in the depth direction.

  FIG. 16 shows the degree of stress concentration in four stages similar to FIG. 14, using FIG. 9 which is a cross-sectional view of the bridge portion 30 when the crushing punch 50 in the mold 40 according to the present embodiment is used. FIG. In FIG. 9, the portion corresponding to the pin angle 116P of the prior art is an arc-shaped inclined portion 58P having a large notch radius, and the cross-sectional shape of the bridge portion 30 gradually changes in the plate thickness direction. Furthermore, since the magnetic material is easy to flow from the bridge portion 30 side toward the hole 22 as indicated by the black arrow 84S, the degree of stress concentration remains at the hatched level. Thus, by using the rotor core manufacturing mold 40 according to the present embodiment, the retention of the plastic flow of the magnetic material can be suppressed and the stress concentration in the magnetic thin plate can be alleviated as compared with the prior art.

  10 (sheet-like) magnetic thin plate, 12 hole assembly, 14 center hole, 16 outer punch hole, 18 core piece, 20, 21, 22, 24 hole, 22S side surface, 22S ′ triangle surface, 26 magnetic pole center line , 30, 31 Bridge part, 32P Punch center line, 32S Bridge center line, 40 (for manufacturing rotor core) Die, 42 Dies part, 44 Punch part, 44 Work hardened surface, 50, 51, 100, 110 Crushing punch, 52P, 54P, 102P, 104P, 112P, 114P Punch surface, 52S, 54S Work hardening surface, 53P, 53S, 62P, 62S Flat surface, 56P, 56S, 106P Flat stepped portion, 58P, 58S, 108P Arc-shaped inclined portion, 60P, 66P stepped wall surface, 64P, 64S centerline side inclined surface, 68P, 68S, 70P, 70S arcuate curved surface, 0P, 80S uneven grooves, 82S, 84S, 82P, 84P filled arrow, 86 machining tool, 90, 94 the contour, 92 discontinuities, 116P, 116S pin angle.

Claims (1)

A die portion used for the rotor core and supporting the back surface of the magnetic thin plate having a plurality of holes;
A punch part having a crushing punch that plastically flows by crushing the elongated bridge part from the upper surface side corresponding to the elongated bridge part between the adjacent holes of the magnetic thin plate supported by the die part; and
With
The crushing punch has an arcuate inclined portion in which the width dimension is gradually narrowed and the height dimension is gradually lowered as it goes to the elongated extending end side,
The surface of the crushing punch has a coefficient of friction when the magnetic material plastically flows in the first direction from the bridge portion toward the hole, and the magnetic material flows plastically in the second direction perpendicular to the first direction. A mold for manufacturing the rotor core, which is smaller than the friction coefficient.

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