JP2016184991A - Magnet embedded type rotor and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet embedded type rotor capable of suppressing reduction in torque of a motor caused by assembling a cover for splash prevention.SOLUTION: A magnet embedded type rotor 4 includes: a cylindrical rotor core 40; each permanent magnet 50 embedded in the rotor core 40; and a cylindrical cover 60 disposed at an outer circumference of the rotor core 40. To the rotor core 40, the cover 60 is integrally fastened while dust is compressed and molded.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a magnet-embedded rotor and a method for manufacturing a magnet-embedded rotor.

  An IPM motor (Interior Permanent Magnet Motor) having a structure in which a permanent magnet for a field is embedded in a rotor is known. As an embedded magnet type rotor used in this IPM motor, there are those using a powder magnetic core obtained by compressing and hardening a magnetic powder whose surface is covered with an insulating film, in addition to a stack of a plurality of electromagnetic steel plates. is there. However, the magnet-embedded rotor using the powder magnetic core is more fragile than those in which magnetic steel sheets are stacked, and there is a concern that the rotor may be scattered by centrifugal force at high speed rotation.

  Therefore, in a magnet-embedded rotor using a dust core, a strength is improved by providing a reinforcing layer on the outer periphery of the rotor. For example, a method described in Patent Document 1 is known as a method for manufacturing a magnet-embedded rotor using the dust core. Patent Document 1 discloses that a reinforcing layer is provided on the outer periphery of the rotor by subjecting the surface of the dust core after molding to heat treatment.

JP 2005-318760 A

  By the way, as a manufacturing method of a magnet embedded type rotor using such a dust core, in addition to the method disclosed in Patent Document 1, a cover for preventing dust core scattering is assembled on the outer periphery of the rotor. There is also a method of providing a reinforcing layer on the outer periphery of the rotor. However, when the cover is assembled to the rotor, a clearance is generated between the rotor and the cover. Further, it is necessary to set a wide air gap between the rotor and the stator in order to prevent contact between the cover and the stator. These clearances and air gaps become magnetic resistances, and the motor torque must be reduced.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnet-embedded rotor and a magnet-embedded mold that can suppress a reduction in torque of a motor caused by assembling a cover for preventing scattering. It is in providing the manufacturing method of a rotor.

  In order to solve the above problems, a magnet-embedded rotor includes a cylindrical rotor core, a permanent magnet embedded in the rotor core, and a cylindrical cover disposed on the outer periphery of the rotor core. The rotor core is a dust core in which the cover is integrally fixed while the dust is compression molded.

  Moreover, about the manufacturing method of the said magnet-embedded rotor, the 1st process which installs a cylindrical cover in a shaping | molding die, and the 2nd which fills a dust in a cover except the part which a permanent magnet is embedded. And a third step of forming a rotor core to which the cover is integrally fixed by compressing the cover and the compact from the axial direction of the cover.

  According to the above configuration and manufacturing method, even when a cover for preventing the dust core from scattering is disposed, the cover can be fixed to the rotor core without causing a clearance between the rotor core and the cover. it can. Therefore, it is possible to suppress a reduction in motor torque due to the clearance between the rotor core and the cover.

  Further, according to the above-described method of manufacturing a magnet-embedded rotor, since the cover is integrally fixed to the rotor core when the rotor core is molded, the process of assembling the cover to the rotor core is unnecessary, and the process can be simplified.

  By the way, since the magnetic permeability of the powder magnetic core constituting the rotor core is higher than that of air, the short core magnetic path including the cover includes a short-circuit magnetic path in which the magnetic flux emitted from the N pole of the permanent magnet enters the S pole without linking the stator coil. There is a concern that the leakage magnetic flux may increase due to being formed by.

  On the other hand, in the above-described magnet-embedded rotor, the permanent magnet is provided with a linear portion extending along the radial direction of the rotor core, and the cover is a portion corresponding to the outer end portion of the linear portion on the outer periphery side of the rotor core in the circumferential direction. It is effective to form a low magnetic permeability portion having a lower magnetic permeability than other portions.

  According to this configuration, since the low magnetic permeability portion is disposed at a position corresponding to the portion where the short-circuit magnetic path of the rotor core is formed, the leakage magnetic flux due to the short-circuit magnetic path can be reduced. Thereby, the ratio of the magnetic flux which contributes to the torque generation of a motor can be raised, and efficiency can be achieved.

Specifically, it is effective that such a low magnetic permeability portion is formed by a plurality of grooves extending in the circumferential direction on the outer peripheral surface of the cover.
In addition, in the magnet-embedded rotor, the permanent magnet is a bonded magnet, the outer end of the linear portion on the outer periphery side of the rotor core is in contact with the inner peripheral surface of the cover, and the low magnetic permeability portion is injected by the bonded magnet. When embedded in the rotor core by molding, it is effective that the portion of the cover that contacts the permanent magnet is formed by plastic deformation.

  In this case, in the above-described method for manufacturing a magnet-embedded rotor, when the low magnetic permeability portion is formed, it is not necessary to position the cover with respect to the rotor core. Therefore, the low magnetic permeability portion extends in the circumferential direction on the outer peripheral surface of the cover. The first process can be simplified as compared with the case where the plurality of grooves are formed.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the torque of the motor by assembling the cover for scattering prevention can be suppressed.

Sectional drawing which shows the cross-section of an IPM motor using a magnet embedded rotor. The perspective view which shows a cover. The perspective view which shows the perspective structure of the magnet embedded type rotor in 1st Embodiment. Sectional drawing explaining the manufacturing apparatus of a magnet embedded type rotor. Sectional drawing explaining the 1st process of the manufacturing method of a magnet embedded type rotor. Sectional drawing explaining the 2nd process of the manufacturing method of a magnet embedded type rotor. Sectional drawing explaining the 3rd process of the manufacturing method of a magnet embedded type rotor. Sectional drawing explaining the process of taking out the manufacturing method of a magnet embedded type rotor. Sectional drawing explaining the process of taking out the manufacturing method of a magnet embedded rotor similarly. The top view which shows the aspect by which a magnet is embedded in the magnet embedded type rotor in 2nd Embodiment. The perspective view which shows the perspective structure of the magnet embedded type rotor in 2nd Embodiment.

(First embodiment)
First, the structure of an IPM motor using the magnet-embedded rotor of this embodiment will be described.

  As shown in FIG. 1, this IPM motor includes a stator 2 fixed to the inner peripheral surface of a housing 1 and a motor as a rotating shaft supported by a housing 1 via a bearing (not shown) so as to be rotatable around an axis m. A shaft 3 and a rotor 4 that is integrally attached to the outer periphery of the motor shaft 3 and disposed inside the stator 2 are provided.

  The stator 2 is formed in a cylindrical shape around the axis m. The stator 2 has a structure in which a plurality of electromagnetic steel plates are laminated in the axial direction. Twelve teeth 20 extending radially inward are formed on the inner peripheral surface of the stator 2. A stator coil 21 is wound around each tooth 20.

The rotor 4 includes a rotor core 40 formed in a cylindrical shape around the axis m, and ten permanent magnets 50 embedded in the rotor core 40.
The rotor core 40 is a dust core obtained by compressing a magnetic powder (dust) whose surface is covered with an insulating coating and hardening it into a cylindrical shape. Such a dust core has a higher permeability than air. The rotor core 40 includes a cylindrical tubular portion 41 centering on the axis m. The motor shaft 3 is inserted into a shaft hole 41 a formed at the center of the cylindrical portion 41.

  In the cylindrical portion 41, ten magnet insertion holes 42 penetrating in the axial direction are formed at equal intervals in the circumferential direction. The cross-sectional shape of each magnet insertion hole 42 orthogonal to the axial direction of the tubular portion 41 is a V-shape that opens toward the outer peripheral side of the tubular portion 41. The magnet insertion hole 42 includes a pair of straight portions 42 a and 42 a extending along the radial direction of the tubular portion 41, and these straight portions 42 a and 42 a intersect at a predetermined angle on the inner peripheral side of the tubular portion 41. . Further, the straight portion 42 a in this embodiment does not reach the outer peripheral surface of the tubular portion 41, and is between the outer end portion 42 b on the outer peripheral side of the tubular portion 41 of the straight portion 42 a and the outer peripheral surface of the tubular portion 41. A bridge portion 70 is formed. A permanent magnet 50 having the same cross-sectional shape is inserted into these magnet insertion holes 42. Each permanent magnet 50 is made of a bonded magnet, and has an N-pole or S-pole inside the V-shape and an S-pole or N-pole outside the V-shape. By these permanent magnets 50, the rotor 4 has a 10-pole structure in which N poles and S poles are alternately arranged along the circumferential direction in the outer circumferential direction.

  As shown in FIGS. 1 and 3, a cylindrical cover 60 made of a magnetic material for preventing scattering of the cylindrical portion 41 in the rotor core 40 is fixed to the outer periphery of the cylindrical portion 41. The magnetic body has a higher magnetic permeability than air. As shown in FIG. 2, the cover 60 has ten low magnetic permeability portions 61 formed at equal intervals in the circumferential direction. The low magnetic permeability portion 61 is configured by arranging a plurality of elongated grooves 61 a extending in the circumferential direction on the outer peripheral surface of the cover 60 over the entire axial direction of the cover 60. The low magnetic permeability portion 61 forms an air layer having a lower magnetic permeability than that of the magnetic body (cover 60) by forming a portion where the groove 61a is formed thinner than other portions. Therefore, the low magnetic permeability portion 61 has a lower magnetic permeability than portions other than the low magnetic permeability portion 61.

  As shown in FIG. 3, each low magnetic permeability portion 61 is disposed at a position corresponding to the bridge portion 70 in a state where the cover 60 is fixed to the rotor core 40. Specifically, the low magnetic permeability portion 61 is disposed in a region straddling the two bridge portions 70, 70 adjacent to each other in the circumferential direction of the tubular portion 41, and corresponds to the opening portion of the V-shaped magnet insertion hole 42. Is not placed.

  In the IPM motor configured as described above, when an alternating current is supplied to the stator coil 21 shown in FIG. 1, a rotating magnetic field is formed. Torque is applied to the rotor 4 by the action of this rotating magnetic field and the magnetic field formed by each permanent magnet 50, and the motor shaft 3 that is a rotating shaft fixed to the rotor 4 rotates.

Next, a method for manufacturing the rotor 4 will be described together with its operation.
As shown in FIG. 4, the manufacturing apparatus 80 for forming the rotor 4 includes an intermediate die 81, a lower die 82, and an upper die 83 that constitute a forming die.

  The middle die 81 is a die that molds the outer peripheral surface of the rotor 4, and a cylindrical portion 81 a is formed in a cylindrical shape. The axial length of the cylindrical portion 81 a is formed larger than the axial length of the rotor 4. The inner diameter of the cylindrical part 81 a coincides with the outer diameter of the rotor 4. The middle mold 81 is fixed at a predetermined position of the manufacturing apparatus 80.

  The lower mold 82 includes an end surface mold portion 82a that molds one end surface in the axial direction of the rotor 4, a shaft hole pin 82b that molds the shaft hole 41a of the rotor 4, and ten magnets that mold each magnet insertion hole 42. And a hole pin 82c. The end surface mold part 82a has a columnar shape, and its outer diameter is large enough to fit into the cylindrical mold part 81a. A shaft hole pin 82b is arranged at the center of the upper surface of the end face mold portion 82a, and each magnet hole pin 82c is arranged at equal intervals in the circumferential direction around the shaft hole pin 82b around the shaft hole pin 82b. ing. The shaft hole pin 82 b and each magnet hole pin 82 c are formed longer than the axial length of the rotor 4. The lower die 82 is disposed below the cylindrical portion 81a of the middle die 81 and is installed so as to reciprocate in the axial direction with respect to the cylindrical portion 81a of the middle die 81.

  The upper mold 83 includes an end surface mold portion 83 a that molds the other end surface of the rotor 4 in the axial direction. The end face mold portion 83a has a columnar shape, and its outer diameter is a size that can be fitted into the cylindrical mold portion 81a. A shaft hole pin fitting portion 83b into which the shaft hole pin 82b can be fitted is formed in the end face mold portion 83a at a position facing the shaft hole pin 82b of the lower die 82. Further, the end face mold portion 83a is formed with a magnet hole pin fitting portion 83c in which each magnet hole pin 82c can be fitted at a position facing each magnet hole pin 82c of the lower die 82. The upper die 83 is disposed on the upper side of the cylindrical portion 81a of the middle die 81 and is installed so as to reciprocate in the axial direction with respect to the cylindrical portion 81a of the middle die 81. When the upper die 83 is close to the lower die 82, the shaft hole pin 82b and the magnet hole pin 82c can be fitted in the shaft hole pin fitting portion 83b and the magnet hole pin fitting portion 83c, respectively. Further, the upper die 83 is separated from the lower die 82, whereby the shaft hole pin 82b and the magnet hole pin 82c fitted in the shaft hole pin fitting portion 83b and the magnet hole pin fitting portion 83c, respectively, The shaft hole pin fitting portion 83b and the magnet hole pin fitting portion 83c can be separated.

  As shown in FIG. 5, the lower mold 82 moves relative to the middle mold 81 and is disposed at the lower end of the cylindrical part 81a, so that a cylindrical space G with a bottom is formed in the cylindrical part 81a. The In the first step, the cover 60 is disposed along the inner peripheral surface of the cylindrical portion 81a. In this first step, each low magnetic permeability portion 61 of the cover 60 is positioned so as to correspond to the bridge portion 70 and is installed in the space G. That is, the cover 60 is installed to face the corresponding portion of each magnet hole pin 82c corresponding to the outer end portion 42b of the linear portion 42a constituting the magnet insertion hole 42.

  As shown in FIG. 6, in the second step after the first step, the space G is filled with the green compact 90. Thereafter, as shown in FIG. 7, in the third step, the upper mold 83 is moved so that the end face mold portion 83a is fitted into the cylindrical mold portion 81a, and the shaft hole pin 82b and each magnet hole pin 82c are shaft holes. It fits in the pin fitting part 83b and each magnet hole pin fitting part 83c. In this third step, the dust core 90 is compressed together with the cover 60 in the space G with a predetermined clamping pressure, whereby the rotor core 40 (cylindrical portion 41) of the dust core in which the cover 60 is integrally fixed without a gap. ) Is formed.

  As shown in FIGS. 8 and 9, after the third step, the upper die 83 is moved in a direction away from the lower die 82, and the shaft hole pin fitting portion 83b and the magnet hole pin fitting portion 83c are moved. The shaft hole pin 82b and the magnet hole pin 82c fitted to each are separated from the shaft hole pin fitting part 83b and the magnet hole pin fitting part 83c. Thereafter, the lower die 82 is moved from the cylindrical portion 81a of the middle die 81, and the rotor core 40 that has been molded is taken out from the cylindrical portion 81a. Further, the rotor core 40 is removed from the lower mold 82 by sliding the rotor core 40 axially upward with respect to the lower mold 82. At this time, the shaft hole 41a and the magnet insertion hole 42 are formed in the position where the shaft hole pin 82b and the magnet hole pin 82c of the rotor core 40 are pulled out.

  Then, after embedding a magnet material before magnetization in each magnet insertion hole 42 of the rotor core 40 taken out by injection molding, the magnet material is oriented and magnetized using an orientation magnetizing device. Through such an orientation and magnetization process, the magnet material becomes the permanent magnet 50, and the manufacture of the rotor 4 is completed.

According to the rotor 4 and the method for manufacturing the rotor 4 described above, the following operations and effects (1) and (2) can be obtained.
(1) According to the rotor 4 manufactured by the manufacturing method shown in FIGS. 5 to 9, the cover 60 for preventing the cylindrical portion 41 (dust core) from being scattered is disposed on the rotor core 40. In addition, the cover 60 can be fixed to the rotor core 40 without causing a clearance between the rotor core 40 and the cover 60. Therefore, it is possible to suppress a decrease in motor torque due to the clearance between the rotor core 40 and the cover 60.

  Further, according to the manufacturing method, since the cover 60 is integrally fixed to the rotor core 40 when the rotor core 40 is molded, the process of assembling the cover 60 to the rotor core 40 is unnecessary, and the process can be simplified.

  (2) By the way, since the magnetic permeability of the cylindrical part 41 (powder magnetic core) which comprises the rotor core 40 is higher than air, the magnetic flux emitted from the N pole of each permanent magnet 50 does not interlink with the stator coil 21. There is a concern that the leakage magnetic flux increases when the short-circuit magnetic path entering the S pole is formed by the bridge portion 70 including the cover 60.

  On the other hand, the rotor 4 according to the present embodiment can reduce the leakage magnetic flux due to the short-circuit magnetic path because the low magnetic permeability portion 61 of the cover 60 is disposed at a position corresponding to the bridge portion 70 of the rotor core 40. . Thereby, the ratio of the magnetic flux which contributes to the torque generation of a motor can be raised, and efficiency can be achieved.

(Second Embodiment)
In the present embodiment, the same configuration and the same control content as those of the embodiment described above are denoted by the same reference numerals, and the redundant description thereof is omitted.

  As shown in FIGS. 10 and 11, a cylindrical cover 62 is fixed to the outer periphery of the cylindrical portion 41. In the present embodiment, the straight portion 43 a constituting each magnet insertion hole 43 having a V-shaped cross section reaches the outer peripheral surface of the cylindrical portion 41, and the outer end portion 43 b of the straight portion 43 a is the inner peripheral surface of the cover 62. Abut. That is, the outer end 43b of the linear portion 43a is closed by the cover 62. Therefore, when the permanent magnet 50 is inserted into the magnet insertion hole 43, the permanent magnet 50 is integrally fixed on the inner peripheral surface of the cover 62.

  As shown in FIG. 11, the cover 62 has plastic deformation portions 63 at equal intervals in the circumferential direction. The plastic deformation portion 63 is formed in a portion where the permanent magnet 50 is fixed on the inner peripheral surface of the cover 62. Specifically, the plastic deformation portion 63 is configured such that when the magnet material is embedded in each magnet insertion hole 43 of the rotor core 40 taken out from the manufacturing apparatus 80 by injection molding, the magnet insertion hole 43 in the cover 62 is subjected to pressure by injection molding. It is formed by plastically deforming so that the part which closes swells radially. The plastic deformation portion 63 formed by plastic deformation becomes a low magnetic permeability portion having a lower magnetic permeability than other portions of the rotor core 40.

  In such a method for manufacturing the rotor 4, since positioning in the circumferential direction when placing the cover 62 in the space G of the manufacturing apparatus 80 is not required in the first step, the first step is more than the first embodiment. Can be simplified.

In addition, each said embodiment can also be implemented with the following forms.
The shape and arrangement of each permanent magnet 50 embedded in the rotor core 40 can be changed as appropriate. The cross-sectional shape orthogonal to the axial direction of the cylindrical portion 41 of each permanent magnet 50 may be, for example, a U shape or a U shape.

  In each of the above embodiments, a bonded magnet is used as each permanent magnet 50. However, for example, a sintered magnet or a compression-molded magnet may be used. When using a sintered magnet, the sintered magnet as a magnet material inserted into the magnet insertion holes 42 and 43 is fixed with a resin material such as an adhesive after the third step of each of the above embodiments.

In the manufacture of the rotor 4, the magnet material may be injection molded and oriented and magnetized in the manufacturing apparatus 80.
-The shaft hole pin 82b, the magnet hole pin 82c, the shaft hole pin fitting portion 83b, and the magnet hole pin fitting portion 83c of the manufacturing apparatus 80 are eliminated, and the compact 90 is compressed by two-color molding in the third step. The formation of the rotor core 40 by the method and the embedding of the magnet material in the rotor core 40 may be performed simultaneously.

  The end plate provided at the end portion in the axial direction of the rotor 4 may be disposed in the space G in the first step and formed integrally with the rotor core 40 in the same manner as the covers 60 and 62. In particular, when forming the rotor core 40 and embedding the magnet material at the same time by two-color molding or the like, the end plates can be disposed on both sides in the axial direction of the rotor 4 and integrally molded.

The low magnetic permeability portion 61 may be formed so as to be inclined in the axial direction of the tubular portion 41 and act as a skew.
-In the said 1st Embodiment, although the low-permeability part 61 was formed by the groove | channel 61a, what makes magnetic permeability lower than other parts, such as making it thin over the whole axial direction of the corresponding cylindrical part 41? For example, the method of forming the low magnetic permeability portion 61 is not limited.

  In the second embodiment, the type of magnetic powder may be different between the radially outer portion and the radially inner portion that are separated by each permanent magnet 50. For example, a magnetic powder whose surface is covered with an insulating coating is used for the inner portion in the radial direction, while a magnetic powder whose surface is not covered with an insulating coating is used for the outer portion in the radial direction. Good. In this case, at the outer portion in the radial direction, the magnetic powder does not have an insulating coating, so that the magnetic permeability can be increased and the torque can be increased compared to the inner portion in the radial direction, contributing to the miniaturization of the motor. To do. Instead of the magnetic powder whose surface is not covered with the insulating coating, a sintered member obtained by baking and solidifying the magnetic powder may be used.

In each of the above embodiments, the 10 pole 12 slot IPM motor is used, but the number of poles and the number of slots are not limited to this, and can be arbitrarily set.
In each of the above-described embodiments, even if the magnetic permeability of the bridge portion 70 is not lower than that of other portions of the rotor core 40, the effect (1) is at least achieved.

The covers 60 and 62 may be an insulating material such as a resin material.
-Although each said embodiment was implement | achieved as a motor using an IPM rotor, you may implement | achieve as a generator using an IPM rotor.

  DESCRIPTION OF SYMBOLS 3 ... Motor shaft (rotating shaft), 4 ... Magnet embedded rotor, 40 ... Rotor core, 41 ... Cylindrical part, 42, 43 ... Magnet insertion hole, 42a, 43a ... Linear part, 42b, 43b ... Outer edge part, DESCRIPTION OF SYMBOLS 50 ... Permanent magnet, 60, 62 ... Cover, 61 ... Low magnetic permeability part, 61a ... Groove, 63 ... Plastic deformation part (low magnetic permeability part) 70 ... Bridge part, 80 ... Manufacturing apparatus, 81 ... Medium type (molding die) , 82 ... lower mold (molding mold), 83 ... upper mold (molding mold), 90 ... green compact.

Claims (5)

A cylindrical rotor core;
A permanent magnet embedded in the rotor core;
A cylindrical cover disposed on the outer periphery of the rotor core,
The rotor core is a magnet-embedded rotor, which is a dust core in which the cover is integrally fixed while dust is compression-molded. The permanent magnet includes a linear portion extending along the radial direction of the rotor core,
2. The magnet embedding according to claim 1, wherein the cover is formed with a low magnetic permeability portion having a lower magnetic permeability than other portions at a portion corresponding to an outer end portion of the linear portion on the outer peripheral side of the linear portion in the circumferential direction. Type rotor.   The embedded magnetic rotor according to claim 2, wherein the low magnetic permeability portion is formed by a plurality of grooves extending in a circumferential direction on an outer peripheral surface of the cover. The permanent magnet is a bonded magnet,
The outer end portion of the linear portion is in contact with the inner peripheral surface of the cover,
The embedded magnet according to claim 2, wherein the low magnetic permeability portion is formed by plastic deformation of a portion of the cover that contacts the permanent magnet when the bonded magnet is embedded in the rotor core by injection molding. Type rotor. A first step of installing a cylindrical cover in the mold;
A second step of filling the cover with green compact except for the portion where the permanent magnet is embedded;
And a third step of forming a rotor core to which the cover is integrally fixed by compressing the cover and the dust from the axial direction of the cover.