JP2021019411A - Rotor for electric motor and manufacturing method therefor - Google Patents

Abstract

To provide a rotor for an electric motor and a manufacturing method therefor, the rotor including respective magnetic poles from which leakage flux is reduced.SOLUTION: A rotor 1 comprises: an iron core 10, a laminate of iron core pieces 11; and a permanent magnet 20 buried in the iron core 10. In an arc-shaped region R extending in the circumferential direction on the outer circumferential side of each iron core piece 11, punching holes PH2 to PH8 are provided in parallel. The region R is partitioned into a first region Ra and a second region Rb separated from the first region Ra so as to take the punching holes PH2 to PH8 provided in parallel as a boundary. In addition, a plurality of bridge parts BR2 stretched between the first region Ra and the second region Rb are formed. The width WBR2 of at least one bridge part BR2 of the plurality of bridge parts BR2 is equal to or shorter than twice the thickness T11 of the iron core piece 11.SELECTED DRAWING: Figure 6

Description

The present invention relates to a rotor of an electric motor and a method for manufacturing the same.

For example, Patent Document 1 below describes a rotor of an electric motor (hereinafter, simply referred to as a rotor). The rotor comprises an iron core and a plurality of permanent magnets. The iron core is a columnar part.

The permanent magnet is a flat plate-shaped member extending parallel to the extending direction of the central axis of the iron core. Permanent magnets are magnetized in the plate thickness direction. That is, the front surface of the permanent magnet is the north pole and the back surface is the south pole. The permanent magnet is embedded in the outer peripheral edge of the iron core. A plurality of permanent magnets are arranged at predetermined intervals in the circumferential direction of the iron core. As a result, a plurality of magnetic poles (N pole and S pole) are arranged at equal intervals in the circumferential direction of the iron core. A plurality of voids are provided at predetermined positions around each permanent magnet inside the iron core.

The iron core is a laminated body in which a plurality of disc-shaped iron core pieces formed by punching a steel plate (base material) are laminated. A plurality of punching holes are arranged side by side in each iron core piece. A bridge portion extending in a predetermined direction is formed between two adjacent punch holes. In other words, in the steel plate (base material), the portions on both sides of the portion left as the bridge portion are punched out. All the iron core pieces are laminated so that the punched holes of each iron core piece communicate with the punched holes of the iron core pieces adjacent to the iron core piece. Permanent magnets are housed in predetermined through holes among the plurality of through holes (portions in which the punched holes communicate) formed in this manner, and the other through holes are left as voids. The internal space of the through hole in which the permanent magnet is housed is not occupied by the permanent magnet, but a part of the through hole is left as a gap.

Japanese Unexamined Patent Publication No. 2012-165480

The magnetic permeability of the above-mentioned void is lower than the magnetic permeability of the surrounding portion (the portion made of the steel plate). By providing the above-mentioned voids around the permanent magnet, it becomes difficult to form a loop-shaped magnetic path from one magnetic pole of the permanent magnet to the other magnetic pole. That is, the leakage flux (short circuit of the magnetic flux) of each magnetic pole of the rotor can be suppressed. However, since a magnetic path passing through the bridge portion is formed, some leakage flux is generated.

The present invention has been made to address the above problems, and an object of the present invention is to provide a rotor of an electric motor in which the leakage flux of each magnetic pole is reduced, and a method for manufacturing the rotor. In the following description of each component of the present invention, in order to facilitate understanding of the present invention, the reference numerals of the corresponding parts of the embodiments are described in parentheses, but each component of the present invention is described. It should not be construed as limited to the configuration of the corresponding parts indicated by the reference numerals of the embodiments.

In order to achieve the above object, the rotors (1, 1B) of the electric motor according to the present invention are a laminated body of a plurality of iron core pieces (11, 11B) which are disc-shaped punched bodies made of steel plates. A cylindrical iron core (10, 10B) and a permanent magnet (20) extending parallel to the extending direction of the central axis of the iron core piece and embedded in the iron core are provided.
A plurality of punching holes (PH2 to PH9) are arranged side by side in an arc-shaped region (R) extending in the circumferential direction on the outer peripheral side of the iron core piece, and the arc-shaped region is formed by the plurality of juxtaposed arc-shaped regions. With the punched hole as a boundary, it is divided into a first region (Ra) and a second region (Rb) separated from the first region, and is bridged between the first region and the second region. A plurality of bridge portions (BR1 to BR6) are formed.
Further, the width (W _BR2 , W _BR4, W _BR5 ) of at least one of the plurality of bridge portions is not more than twice the plate thickness (T ₁₁ ) of the iron core piece.
In this case, the iron core may have a plurality of communication portions (TH2 to TH8) in which the plurality of punched holes of each iron core piece communicate with the plurality of punched holes of adjacent iron core pieces.
Further, the permanent magnet is housed in at least one communication part (TH2, TH8) of the plurality of communication parts, and one magnetic pole of the permanent magnet is in the communication part in which the permanent magnet is housed. It is preferable that the other magnetic pole of the permanent magnet is directed to the one region side, the other magnetic pole of the permanent magnet is directed to the second region side, and a predetermined portion in the communication portion in which the permanent magnet is housed is a gap (G).

In the rotor of the electric motor according to one aspect of the present invention, among the plurality of bridge portions, the first bridge portion (BR2, BR5) constituting the first magnetic path among the magnetic paths of the permanent magnets. The width (W _BR2 , W _BR5 ) is set to be smaller than the width (W _BR3 , W _BR6 ) of the second bridge portion (BR3, BR6) constituting the second magnetic path longer than the first magnetic path. Has been done.

Further, in the rotor of the electric motor according to another aspect of the present invention, the bridge portion which is at least one bridge portion and whose width is twice or less the plate thickness of the iron core piece is from the permanent magnet. As seen, they are arranged inside the iron core piece in the radial direction.

Further, in order to achieve the above object, the method for manufacturing the rotor of the electric motor according to the present invention includes a core piece manufacturing process for punching a steel plate to manufacture a plurality of disk-shaped iron core pieces, and the plurality of iron cores. An iron core manufacturing process in which pieces are laminated to produce a columnar iron core, and a permanent magnet assembly in which a plurality of permanent magnets extended parallel to the extending direction of the central axis of the iron core piece are embedded in the iron core. Including the process.
In the iron core piece manufacturing process, a plurality of punched holes are arranged side by side in an arc-shaped region extending in the circumferential direction on the outer peripheral side of the iron core piece, and the arc-shaped region is defined by the plurality of punched holes. , A step of dividing into a first region and a second region separated from the first region, and forming a plurality of bridge portions bridged between the first region and the second region. The step of punching the steel plate so that the width of at least one of the plurality of bridge portions is not more than twice the plate thickness of the iron core piece is included.
In this case, in the iron core manufacturing process, the plurality of iron cores are formed so that the plurality of punched holes of each iron core piece communicate with each of the plurality of punched holes of the adjacent iron core pieces. It is preferable to include a step of laminating the pieces.
Further, the permanent magnet assembling step is a step of accommodating the permanent magnet in at least one communicating portion among the plurality of communicating portions, and in the communicating portion in which the permanent magnet is accommodated, the permanent magnet One magnetic pole is directed toward the first region, the other magnetic pole of the permanent magnet is directed toward the second region, and a gap is formed at a predetermined portion in the communication portion in which the permanent magnet is housed. As described above, it is preferable to include a step of arranging the permanent magnets.

If a predetermined portion of the steel plate (base material) is punched so that the width of the bridge portion is larger than twice the plate thickness of the iron core piece, residual stress is generated at both ends in the width direction of the bridge portion. Although it is distributed, residual stress is not distributed in the central part of the bridge part.

On the other hand, in the manufacturing process of the iron core piece of the rotor of the electric motor according to the present invention, the steel plate (base material) is specified so that the width of at least one bridge portion is not more than twice the plate thickness of the iron core piece. The part of is punched out. In this case, work hardening occurs over substantially the entire bridge portion, and residual stress is distributed not only at both ends in the width direction of the bridge portion but also at the center portion.

In general, it is known that in a steel sheet, a portion where residual stress is distributed is more difficult for magnetic flux to pass through (that is, has a lower magnetic permeability) than a portion where residual stress is not distributed.

The iron core piece of the rotor of the electric motor according to the present invention has a plurality of bridge portions, and the width of at least one of the bridge portions is not more than twice the plate thickness of the iron core piece. Therefore, the residual stress is distributed over the entire bridge portion. Therefore, according to the present invention, the leakage flux can be reduced as compared with the case where the width of all the bridge portions is twice or more the plate thickness of the iron core piece. For example, a bridge portion in a conventional iron core piece whose width is larger than twice the plate thickness may be replaced (divided) with a plurality of bridge portions. However, the width of at least one of the bridge portions is set to be twice or less the plate thickness, and the total cross-sectional area of the plurality of bridge portions replaced is the same as the cross-sectional area of the original bridge portion. Set. According to this, the region where the residual stress is distributed in the entire of the plurality of replaced bridge portions is larger than the region where the residual stress is distributed in the original bridge portion. For example, if the widths of all the bridge portions of the plurality of bridge portions are set to twice or less the plate thickness, the residual stress is distributed over the entire of the replaced plurality of bridge portions. Therefore, the leakage flux passing through the replaced plurality of bridge portions is reduced as compared with the leakage flux passing through the original bridge portion.

It is a perspective view of the main part of the electric motor to which the rotor which concerns on one Embodiment of this invention is applied. It is a perspective view of the rotor which concerns on one Embodiment of this invention. It is a perspective view of the iron core which constitutes the rotor of FIG. It is a perspective view of the permanent magnet which constitutes the rotor of FIG. It is a top view of the iron core piece constituting the iron core of FIG. FIG. 5 is an enlarged view of a part of the iron core piece of FIG. 5, and is an enlarged plan view of one of eight regions obtained by dividing the outer peripheral edge of the iron core piece into eight equal parts in the circumferential direction. It is an enlarged plan view which enlarged one magnetic pole of a rotor. It is a perspective view of the rotor which concerns on a comparative example. It is a perspective view of the iron core of the rotor of FIG. It is a top view of the iron core piece constituting the iron core of FIG. FIG. 10 is an enlarged view of a part of the iron core piece of FIG. 10, and is an enlarged plan view of one of eight regions obtained by dividing the outer peripheral edge of the iron core piece into eight equal parts in the circumferential direction. It is a graph which shows the rate of change of the hardness of the peripheral part of the punched hole of the iron core piece of FIG. 11 (the ratio of the hardness before and after the formation of the punched hole). It is a distribution diagram (EBSD analysis result) of the residual stress in the cross section perpendicular to the longitudinal direction of the bridge portion (BR2A) of the iron core piece of FIG. It is a distribution diagram (EBSD analysis result) of the residual stress in the cross section perpendicular to the longitudinal direction of the bridge portion (BR2) of the iron core piece of FIG. FIG. 5 is a distribution diagram of magnetic field lines at one magnetic pole of the rotor of FIG. 2 and the rotor of FIG. It is a distribution figure of the magnetic field line in one magnetic pole of the rotor which concerns on the 1st modification of this invention. It is an enlarged plan view of the bridge part extending along the outer peripheral surface of one magnetic pole of the rotor which concerns on the 2nd modification of this invention. It is an enlarged plan view of the bridge part extending along the outer peripheral surface of one magnetic pole of the rotor which concerns on the 3rd modification of this invention.

Hereinafter, the rotor 1 according to the embodiment of the present invention will be described. Here, the configuration of the electric motor M to which the rotor 1 is applied will be briefly described. As shown in FIG. 1, the electric motor M includes a stator ST and a rotor 1. The stator ST is a cylindrical component. A plurality of coils are assembled on the inner peripheral surface of the stator ST. These coils are arranged at predetermined intervals in the circumferential direction of the stator ST.

The rotor 1 is a columnar part. The rotor 1 is housed in the stator ST, and the rotor 1 and the stator ST are coaxially arranged. As will be described in detail later, the rotor 1 has a plurality of magnetic poles (N pole and S pole) (see FIG. 2). These magnetic poles are arranged at equal intervals in the circumferential direction of the rotor 1. In this embodiment, the rotor 1 includes eight magnetic poles (four north poles and four south poles). These N poles and S poles are alternately arranged in the circumferential direction of the iron core 10. Power is supplied to the plurality of coils of the stator ST in a predetermined order. As a result, the rotor 1 rotates with respect to the stator ST.

Next, the outline of the configuration of the rotor 1 will be described. As shown in FIG. 2, the rotor 1 includes an iron core 10 and a plurality of (16) permanent magnets 20. As shown in FIG. 3, the iron core 10 is a columnar part. Further, as shown in FIG. 4, the permanent magnet 20 is a flat plate-shaped component extended in parallel with the extending direction of the central axis of the iron core 10. The permanent magnet 20 is magnetized in the plate thickness direction thereof. That is, the front surface 20a of the permanent magnet 20 is the north pole, and the back surface 20b is the south pole. Each part of the iron core 10 divided into eight equal parts in the circumferential direction (described later) so that the above eight magnetic poles (four N poles and four S poles) are arranged in the circumferential direction of the iron core 10. Two permanent magnets 20 are embedded in the laminated portion SR) (see FIG. 2).

Next, the configuration of the iron core 10 will be specifically described. The iron core 10 is a laminated body in which a plurality of iron core pieces 11 are laminated (see FIGS. 3 and 5). The iron core piece 11 is formed by punching a silicon steel plate (base material) (iron core piece manufacturing process). The plate thickness of the silicon steel plate (base material) is, for example, 0.3 mm. The iron core piece 11 is a disk-shaped part (punched molded product).

A punch hole PH1 is formed in the central portion of the iron core piece 11. The punched hole PH1 has a circular shape.

Further, each region R obtained by dividing the outer peripheral edge of the iron core piece 11 (the outer annular portion of the punched hole PH1) into eight equal parts in the circumferential direction of the iron core piece 11 in the circumferential direction of the iron core piece 11. Punch holes PH2 to PH8 are formed in each arcuate (fan-shaped) region R extending in the direction (see FIG. 6). As will be described in detail later, each region R constitutes each magnetic pole of the rotor 1. That is, the regions R and R located on both sides of the region R corresponding to the N pole correspond to the S pole (see FIG. 5).

The punched holes PH2 to the punched holes PH8 are arranged side by side in a direction perpendicular to the center line CL in the circumferential direction of the region R (see FIG. 6).

The punched hole PH2 and the punched hole PH8 are line-symmetrical with respect to the center line CL. Further, the shapes of the punched holes PH3 to the punched holes PH7 are the same. Punch holes PH3 to punch holes PH7 are arranged side by side between the punch holes PH2 and the punch holes PH8.

The punched hole PH2 is composed of a first hole portion PH2a and a second hole portion PH2b. The first hole PH2a has a trapezoidal shape. That is, the first hole PH2a includes a set of sides L1 and L2 extending in a direction perpendicular to the extending direction of the center line CL, and one end of the sides L1 and L2 (the end on the center line CL side). ) And the other end (the end opposite to the center line CL) have a set of sides L3 and L4, respectively. The side L2 is located on the outer side of the iron core piece 11 in the radial direction when viewed from the side L1. The side L2 is longer than the side L1. The side L3 extends parallel to the center line CL and is orthogonal to the sides L1 and L2. The side L4 is inclined with respect to the sides L1 and L2.

The second hole portion PH2b extends from the other end of the side L2 of the first hole portion PH2a (near the intersection of the side L2 and the side L4) toward the outer peripheral side of the region R. The second hole PH2b has a rectangular shape. As will be described later, in a state where the iron core pieces 11 are laminated, the second hole portion PH2b of each iron core piece 11 communicates with the second hole portion PH2b of the iron core piece 11 adjacent to the iron core piece 11, and this communication portion The permanent magnet 20 is inserted into the through hole TH2 (see FIGS. 3 and 7). The length of the short side of the second hole portion PH2b is equivalent to the plate thickness T ₂₀ of the permanent magnet ₂₀ (see FIG. 4). The length of the long side of the second hole portion PH2b is slightly longer than the width _{W 20} of the permanent magnet 20.

The punched holes PH3 to the punched holes PH7 each exhibit a rectangle extending parallel to the extending direction of the center line CL. The punch holes PH3 to the punch holes PH7 have the same shape and size. The punched holes PH3 to the punched holes PH7 are arranged at equal intervals in a direction perpendicular to the extending direction of the center line CL.

The punched hole PH8 is composed of a first hole portion PH8a and a second hole portion PH8b, similarly to the punched hole PH2. The first hole PH8a and the first hole PH2a are line-symmetric with respect to the center line CL, and the second hole PH8b and the second hole PH2b are line-symmetric with respect to the center line CL.

The outer shape (outer peripheral surface) of the iron core piece 11 and the punched holes PH1 to the punched holes PH8 are formed (punched) at the same time.

Punch holes PH2 and punch holes PH8 are arranged side by side in the region R, and the region R is divided into a first region Ra and a second region Rb with the punch holes PH2 to the punch holes PH8 as boundaries. Then, as described below, two bridge portions BR1 and six bridge portions BR2 are bridged between the first region Ra and the second region Rb. The "width" of each bridge portion in the following description is perpendicular to their extension direction (direction from the first region Ra to the second region Rb, or the opposite direction), and is a plate of the iron core piece. It means the dimension in the direction perpendicular to the thickness direction.

Between the tip of the second hole PH2b and the second hole PH8b (the end opposite to the first hole PH2a and the first hole PH8a) and the outer peripheral surface of the iron core piece 11, a silicon steel plate ( Base material) remains. These remaining portions are referred to as bridge portions BR1. Further, a silicon steel plate (base material) remains between two adjacent punched holes in the punched holes PH2 to the punched holes PH8. These remaining portions are referred to as bridge portions BR2. The width W _BR1 of the bridge portion BR1 is larger than twice the plate thickness T ₁₁ of the iron core piece 11. The width W _BR1 of the bridge portion BR1 is, for example, 1.5 mm (> 0.3 mm (plate thickness T ₁₁ ) × 2)). Further, the width W _BR2 of the bridge portion BR2 is twice or less the plate thickness T ₁₁ of the iron core piece 11. The width W _BR2 of the bridge portion BR2 is, for example, 0.5 mm (<0.3 mm (plate thickness T ₁₁ ) × 2)).

A plurality of (for example, 500) iron core pieces 11 configured as described above are laminated and caulked to each other to form an iron core 10 (iron core manufacturing process). In this step, the punched holes PH1 of each iron core piece 11 are coaxially arranged, and each region R of each iron core piece 11 is overlapped with the region R of the iron core piece 11 adjacent to the iron core piece 11. That is, the punched holes PH2 to the punched holes PH8 of each iron core piece 11 communicate with the punched holes PH2 to the punched holes PH8 of the iron core piece 11 adjacent to the iron core piece 11 (the inner peripheral surfaces of the punched holes are continuous). Each iron core piece 11 is arranged in.

As a result, the iron core 10 is formed with a through hole TH1 penetrating from one end surface to the other end surface in the extending direction of the central axis (see FIG. 3). The through hole TH1 is a portion where the punched holes PH1 of the adjacent iron core pieces 11 communicate with each other. The through hole TH1 is coaxially arranged with respect to the central axis of the iron core 10.

Further, the iron core 10 has eight laminated portions SR formed by laminating eight regions R of a plurality of iron core pieces 11. Each laminated portion SR corresponds to the magnetic pole of the rotor 1. Through holes TH2 to through holes TH2 that penetrate from one end surface to the other end surface in the extending direction of the central axis of the iron core 10 are formed in each laminated portion SR. The through hole TH2 is a portion where the first hole portion TH2a, which is a portion where the first hole portion PH2a of the punched hole PH2 of each iron core piece 11 communicates, and the portion where the second hole portion PH2b of the punched hole PH2 of each iron core piece 11 communicates. It is composed of a second hole portion TH2b. Further, in the through hole TH8, the first hole portion TH8a, which is a portion where the first hole portion PH8a of the punched hole PH8 of each iron core piece 11 communicates, and the second hole portion PH8b of the punched hole PH8 of each iron core piece 11 communicate with each other. It is composed of a second hole portion TH8b, which is a formed portion.

A shaft (rotational drive shaft of the electric motor M) (not shown) is inserted into the through hole TH1. Then, the outer peripheral surface of the shaft is adhered to the inner peripheral surface of the through hole TH1.

Further, the permanent magnets 20 are housed in the second hole TH2b and the second hole TH8b of the through holes TH2 and the through holes TH8 provided in each laminated portion SR, and each permanent magnet 20 is a second hole. It is adhered to the inner peripheral surfaces of the portion TH2b and the second hole portion TH8b (permanent magnet assembly step). The surface 20a (N pole) of the permanent magnet 20 is directed toward the first region Ra side of each iron core piece 11 in the second hole portion TH2b and the second hole portion TH8b of the laminated portion SR corresponding to the N pole. The back surface 20b (S pole) of the permanent magnet 20 is directed toward the second region Rb side of each iron core piece 11. On the other hand, in the second hole portion TH2b and the second hole portion TH8b of the laminated portion SR corresponding to the S pole, the surface 20a (N pole) of the permanent magnet 20 is directed toward the second region Rb side of each iron core piece 11. The back surface 20b (S pole) of the permanent magnet 20 is directed toward the first region Ra side of each iron core piece 11.

In each through hole TH2, one end of the permanent magnet 20 in the width direction is located at the boundary between the first hole portion TH2a and the second hole portion TH2b (see FIG. 7). That is, in the through hole TH2, the first hole portion TH2a is left as a gap G along the one end surface 20c in the width direction of the permanent magnet 20. Further, as described above, the width W ₂₀ of the permanent magnet 20 is shorter than the length of the long side of the second hole portion PH2b. Therefore, the internal space of the second hole portion TH2b is not occupied by the permanent magnet 20, but a gap G along the other end surface 20d in the width direction of the permanent magnet 20 is left in the second hole portion TH2b.

Further, in each through hole TH8, one end of the permanent magnet 20 in the width direction is located at the boundary between the first hole portion TH8a and the second hole portion TH8b. That is, in the through hole TH8, the first hole portion TH8a is left as a gap G along the one end surface 20c in the width direction of the permanent magnet 20. Further, the internal space of the second hole portion TH8b is not occupied by the permanent magnet 20, but a gap G along the other end surface 20d in the width direction of the permanent magnet 20 is left in the second hole portion TH8b.

Further, nothing is accommodated in the through hole TH3 to the through hole TH7. That is, the through hole TH3 to the through hole TH7 are left as the gap G.

The bridge portion BR2 is arranged inside the iron core piece 11 (iron core 10) in the radial direction when viewed from the permanent magnet 20.

Each laminated portion SR is composed of a first laminated portion SRa which is a portion where the first region Ra is laminated and a second laminated portion SRb which is a portion where the second region Rb is laminated, and a gap G is provided between them. Are lined up side by side. The magnetic permeability of the void G is smaller than the magnetic permeability of the periphery (the portion made of the silicon steel plate). Therefore, the first laminated portion SRa and the second laminated portion SRb are magnetically separated by the gap G (the magnetic coupling force is weakened). Therefore, it is difficult to form a magnetic path from the first laminated portion SRa side to the second laminated portion SRb side (or in the opposite direction) as compared with the case where the through hole TH2 to the through hole TH8 is not provided in each laminated portion SR. That is, the leakage flux (short circuit of magnetic flux) is reduced at each magnetic pole (stacked portion SR) of the rotor 1. The bridge portion BR1 and the bridge portion BR2 of the iron core piece 11 form a magnetic path, and some leakage flux is generated. However, as described below, due to the action of the residual stress distributed in the bridge portion BR2, the bridge portion BR2 The magnetic flux is difficult to pass through.

Next, in order to explain the action and effect of the bridge portion BR2 of the iron core piece 11, the rotor 1A as a comparative example will be described. As shown in FIG. 8, the rotor 1A includes an iron core 10A and a plurality of permanent magnets 20. As shown in FIG. 9, the iron core 10A is a laminated body in which iron core pieces 11A are laminated. As shown in FIG. 10, the configuration (shape, diameter, plate thickness, etc.) of the iron core piece 11A is the same as that of the iron core piece 11, but the configuration of the punched hole (bridge portion) is different from that of the iron core piece 11. Specifically, the iron core piece 11A has a punching hole PH1A, a punching hole PH2A, and a punching hole PH8A similar to the punching hole PH1, punching hole PH2, and punching hole PH8 of the iron core piece 11. In the iron core piece 11, punching holes PH3 to punching holes PH7 are provided between the punching holes PH2 and the punching holes PH8 (see FIG. 6), but in the iron core piece 11A, the punching holes PH2A and the punching holes PH8A One punch hole PHA is provided between them (see FIG. 11). That is, while the two bridge portions BR1 and the six bridge portions BR2 are provided in one region R of the iron core piece 11, the two bridge portions BR1A and the two bridge portions BR1A are provided in one region R of the iron core piece 11A. Two bridge portions BR2A are provided. The width W _BR1A of the bridge portion _BR1A is the same as the width W _BR1 of the bridge portion BR1 (that is, 1.5 mm). On the other hand, the width W _BR2A of the bridge portion BR2A is the same as the width WBR1A of the bridge portion BR1A (that is, 1.5 mm). That is, the width W _BR2A of the bridge portion BR2A is larger than twice the plate thickness T _11A (= 0.3 mm) of the iron core piece 11A.

The iron core pieces 11A configured as described above are laminated to form the iron core 10A (see FIG. 9). Then, similarly to the rotor 1, the permanent magnet 20 is assembled to the iron core 10A to form the rotor 1A (see FIG. 8).

Next, the leakage flux of the rotor 1 and the rotor 1A is compared. Here, it is generally known that in a steel sheet, a portion where residual stress is distributed is less likely to form a magnetic path (a magnetic permeability is lower) than a portion where residual stress is not distributed. Further, in general, when a punched hole is formed in a steel sheet, it is processed into a region of the remaining part of the steel sheet that has entered the remaining part by a distance equivalent to the plate thickness from the inner peripheral surface (shearing surface) of the punched hole. It is known that hardening occurs (see FIG. 12) and residual stress is distributed in the site.

In the manufacturing process of the iron core piece 11A according to the comparative example, the silicon steel plate (base material) is predetermined so that the width W _BR2A of the bridge portion BR2A is 1.5 mm, which is larger than twice the plate thickness T _11A of the iron core piece 11A. The part of is punched out. In this case, work hardening occurs at both ends of the bridge portion BR2A in the width direction, and residual stress is distributed in the portion (see FIG. 13), but work hardening occurs at the central portion of the bridge portion BR2A. Residual stress is not distributed in the relevant part.

In contrast, in the manufacturing process of the core 11 of the present embodiment, as the width _{W BR2} of the bridge portion BR2 is doubled or less is 0.5mm in thickness _{T 11} of the core piece 11, a silicon steel plate (mother A predetermined part of the material) is punched out. In this case, work hardening occurs over substantially the entire bridge portion BR2, and residual stress is distributed not only at both ends in the width direction of the bridge portion BR2 but also at the central portion (see FIG. 14).

The iron core piece 11 according to the present embodiment corresponds to the one in which the bridge portion BR2A of the iron core piece 11A according to the comparative example is replaced with the bridge portion BR2, BR2, BR2. The total cross-sectional area of the bridge portions BR2, BR2, and BR2 is the same as the cross-sectional area of the bridge portion BR2A. Then, while the residual stress is not distributed in a part of the bridge portion BR2A, the residual stress is distributed over the entire bridge portion BR2, BR2, BR2. Therefore, the leakage flux of each magnetic pole of the rotor 1 is reduced as compared with the rotor 1A. Since the width W _BR1 of the bridge portion _BR1 and the width W _BR1A of the bridge portion _BR1A are the same, the leakage flux passing through the bridge portion BR1 and the leakage flux passing through the bridge portion BR1A are equivalent.

Next, the rigidity of the rotor 1 and the rotor 1A are compared. When the rotors 1 and 1A are rotationally driven, centrifugal force acts on the iron cores 10 and 10A, respectively. The total cross-sectional area of the bridge portion BR1 and the bridge portion BR2 of the region R of the iron core piece 11 is the same as the total cross-sectional area of the bridge portion BR1A and the bridge portion BR2A of the region R of the iron core piece 11A. Further, as described above, work hardening does not occur in the central portion of the bridge portion BR2A in the width direction, whereas work hardening occurs in the entire bridge portion BR2. Therefore, the rigidity of the entire portion consisting of the two bridge portions BR1 and the six bridge portions BR2 provided in the region R of the iron core piece 11 is increased by the two bridge portions BR1A provided in the region R of the iron core piece 11A. And higher than the rigidity of the entire portion consisting of the two bridge portions BR2A. Therefore, the rigidity of the iron core 10 with respect to the above-mentioned centrifugal force (difficulty of deformation such that the first region Ra protrudes outward) is higher than the rigidity of the iron core 10A.

Furthermore, the practice of the present invention is not limited to the above-described embodiment, and various changes can be made as long as the object of the present invention is not deviated.

For example, instead of the iron core piece 11, as shown in FIG. 16, the rotor 1B may be configured by using the iron core 10B in which the iron core pieces 11B are laminated. The iron core piece 11B corresponds to a comparative example in which the bridge portion BR2A of the iron core piece 11A is replaced with the bridge portion BR2 similar to the above embodiment and the bridge portion BR3 described below. The width W _BR3 of the bridge portion BR3 is slightly larger than twice the plate thickness of the iron core piece 11B. For example, the width W _BR3 of the bridge portion BR3 is 1.0 mm (> 0.3 mm (plate thickness) × 2). That is, the width W _BR3 of the bridge portion _BR3 is smaller than the width W _BR2A (= 1.5 mm) of the bridge portion BR2A.

The total cross-sectional area of the bridge portion BR2 and the bridge portion BR3 is the same as the cross-sectional area of the bridge portion BR2A of the iron core piece 11A. There is a region where residual stress is not distributed (work hardening does not occur) in the central portion of the bridge portion BR3 in the width direction, but the region is narrower than that region in the bridge portion BR2A. Therefore, the region where the residual stress is distributed in the entire portion including the bridge portion BR2 and the bridge portion BR3 is larger than the region where the residual stress is distributed in the bridge portion BR2A. Therefore, the leakage flux of each magnetic pole of the rotor 1B is reduced as compared with the rotor 1A.

Further, in the example of FIG. 16, the bridge portion BR2, which is relatively difficult to pass magnetic flux, is arranged in the vicinity of the permanent magnet 20, and the bridge portion BR3, which is slightly easier to pass magnetic flux than the bridge portion BR2, is seen from the permanent magnet 20. It is arranged at a position farther than the bridge portion BR2. That is, the length of the magnetic path passing through the bridge portion BR2 is shorter than the length of the magnetic path passing through the bridge portion BR3. In other words, the bridge portion BR2, which is difficult to pass magnetic flux, is arranged at a position where the magnetic flux density is relatively large, and the bridge portion BR3, which is slightly easier to pass magnetic flux than the bridge portion BR2, is arranged at a position where the magnetic flux density is relatively small. Has been done. According to this, the leakage flux can be reduced more efficiently as compared with the case where the bridge portion BR2 and the bridge portion BR3 are arranged at positions opposite to those in FIG.

Further, the total cross-sectional area of the two bridge portions BR1, the two bridge portions BR2 and the two bridge portions BR3 in the region R of the iron core piece 11B is the two bridge portions BR1A and the two bridge portions BR1A in the region R of the iron core piece 11A. It is the same as the total cross-sectional area of the two bridge portions BR2A. Then, work hardening has occurred over the entire bridge portion BR2. Further, work hardening has occurred at both ends of the bridge portion BR3 in the width direction. As described above, work hardening has not occurred in the central portion of the bridge portion BR3 in the width direction, but the region is narrower than that of the bridge portion BR2A. Therefore, the region where work hardening occurs in the bridge portion (the portion consisting of the two bridge portions BR1, the two bridge portions BR2, and the two bridge portions BR3) provided in the region R of the iron core piece 11B is the iron core. It is larger than the region where work hardening occurs in the bridge portion (the portion composed of the two bridge portions BR1A and the two bridge portions BR2A) provided in the region R of the piece 11A. That is, the rigidity of the entire bridge portion of the region R of the iron core piece 11B is higher than the rigidity of the entire bridge portion of the region R of the iron core piece 11A. That is, the rigidity of the iron core 10B with respect to the centrifugal force is higher than the rigidity of the iron core 10A.

Further, as shown in FIG. 17A, the bridge portion BR1 in the iron core piece 11 of the rotor 1 may be replaced with the bridge portions BR4, BR4, BR4. That is, slit-shaped punched holes PH9 and PH9 may be formed between the punched holes PH2 (PH8) and the outer peripheral surface of the iron core piece 11. The width W _BR4 of the bridge portion BR4 is, for example, 0.5 mm. According to this, the residual stress is distributed over the entire bridge portion BR4. Further, the total cross-sectional area of the bridge portions BR4, BR4, and BR4 is the same as the cross-sectional area of the bridge portion BR1. Therefore, the leakage flux passing through the outer peripheral side of the iron core piece 11 when viewed from the permanent magnet 20 is reduced as compared with the above embodiment (FIG. 7). Further, work hardening has occurred over the entire bridge portion BR4. Therefore, the rigidity of this modification is higher than that of the above embodiment (FIG. 7).

Further, as shown in FIG. 17B, the bridge portion BR1 in the iron core piece 11 may be replaced with the bridge portion BR5 and the bridge portion BR6. The width W _BR5 of the bridge portion BR5 is, for example, 0.5 mm, and the width W _BR6 of the bridge portion _BR6 is, for example, 1.0 mm. According to this, the residual stress is distributed over the entire bridge portion BR5. Further, although there is a region in which the residual stress is not distributed in the central portion in the width direction of the bridge portion BR6, the region is narrower than that of the bridge portion BR1. Further, the total cross-sectional area of the bridge portion BR5 and the bridge portion BR6 is the same as the cross-sectional area of the bridge portion BR1. Therefore, the leakage flux passing through the outer peripheral side of the iron core piece 11 when viewed from the permanent magnet 20 is reduced as compared with the above embodiment (FIG. 7). Further, the region where work hardening occurs in the entire portion including the bridge portion BR5 and the bridge portion BR6 is larger than the region where work hardening occurs in the bridge portion BR1. Therefore, the rigidity of this modification is higher than that of the above embodiment (FIG. 7).

1,1A, 1B ... Rotor 10,10A, 10B ... Iron core, 11,11A, 11B ... Iron core piece, 20 ... Permanent magnet, BR1, BR2, BR3, BR4, BR5, BR6, BR1A, BR2A ... Bridge part, G ... Air gap, M ... Electric motor, PH1-PH9, PH1A, PH2A, PH8A, PHA ... Punch hole, R ... Region, Ra ... 1st region, Rb ... 2nd region, SR ... Laminated part, T _11, T _11A ... Plate thickness, TH1 to TH8 ... Through hole

Claims (4)

A columnar iron core, which is a laminate of a plurality of iron core pieces, which is a disk-shaped punched molded body made of steel plates,
A permanent magnet extending parallel to the extending direction of the central axis of the iron core piece and embedded in the iron core,
It is a rotor of an electric motor equipped with
A plurality of punching holes are arranged side by side in an arc-shaped region extending in the circumferential direction on the outer peripheral side of the iron core piece, and the arc-shaped region is the first with the plurality of punched holes arranged side by side as a boundary. A plurality of bridge portions are formed by being divided into a region and a second region separated from the first region and bridged between the first region and the second region.
A rotor of an electric motor in which the width of at least one of the plurality of bridge portions is not more than twice the plate thickness of the iron core piece. In the rotor of the electric motor according to claim 1,
Among the plurality of bridge portions, the width of the first bridge portion forming the first magnetic path among the magnetic paths of the permanent magnet constitutes the second magnetic path longer than the first magnetic path. The rotor of the electric motor, which is set smaller than the width of the second bridge part. In the rotor of the electric motor according to claim 1 or 2.
The at least one bridge portion whose width is not more than twice the plate thickness of the iron core piece is arranged inside the iron core piece in the radial direction when viewed from the permanent magnet. Rotor of electric motor. An iron core piece manufacturing process that punches out a steel plate to produce multiple disc-shaped iron core pieces,
An iron core manufacturing process for manufacturing a columnar iron core by laminating the plurality of iron core pieces,
A permanent magnet assembling step of embedding a plurality of permanent magnets extending parallel to the extending direction of the central axis of the iron core piece in the iron core.
Is a method of manufacturing a rotor for an electric motor, including
The iron core piece manufacturing process is
A plurality of punching holes are arranged side by side in an arc-shaped region extending in the circumferential direction on the outer peripheral side of the iron core piece, and the arc-shaped region is defined as a first region and the said It is a step of partitioning into a second region separated from the first region and forming a plurality of bridge portions bridged between the first region and the second region, and is a step of forming a plurality of bridge portions of the plurality of bridge portions. A method for manufacturing a rotor of an electric motor, which comprises a step of punching the steel plate so that the width of at least two of the bridge portions is not more than twice the plate thickness of the iron core piece.