JP7528591B2 - Rotor and method for manufacturing the rotor - Google Patents

Description

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

Conventionally, a rotor having a shaft and a laminated core into which the shaft is inserted, and a method for manufacturing the rotor are known (see, for example, Patent Document 1).

The above-mentioned Patent Document 1 discloses a rotor for a motor that includes a hollow rotating shaft having a pipe structure and a laminated core into which the rotating shaft is inserted. The rotating shaft is inserted into a through hole provided in the center of the laminated core. The rotating shaft is provided with a retaining portion formed by a hydroforming method. The retaining portion is formed by expanding the rotating shaft toward the outer diameter side by the hydroforming method. Two retaining portions are provided on one and the other axial sides of the laminated core so as to sandwich the laminated core in the axial direction. In other words, the two retaining portions are provided outside the axial end faces of the laminated core. As a result, the laminated core and the rotating shaft are fixed (positioned) in the axial direction by the two retaining portions, and the rotating shaft is prevented from coming out of the laminated core in the axial direction.

JP 2001-268858 A

However, in the motor rotor described in Patent Document 1, the two retaining portions that secure (position) the laminated core and the rotating shaft are provided outside the axial end faces of the laminated core, which creates the problem that the axial length of the motor rotor is longer by the axial length of the retaining portions.

The present invention aims to provide a rotor and a method for manufacturing the rotor that can prevent the shaft from coming out of the laminated core in the axial direction while preventing the axial length of the rotor from increasing.

In order to achieve the above-mentioned object, a rotor in a first aspect of the present invention comprises a cylindrical shaft, and a laminated core in which a plurality of electromagnetic steel plates are stacked, the plurality of electromagnetic steel plates having a first through hole at the center through which the shaft is inserted, so that a shaft insertion hole in which the shaft is disposed is formed by the first through hole, wherein the first through hole has a non-circular shape when viewed in the axial direction of the laminated core, the laminated core includes a plurality of steel plate blocks formed of a plurality of electromagnetic steel plates stacked such that apexes of the first through holes of a non-circular shape when viewed in the axial direction overlap each other, and has a step-skew structure in which the steel plate blocks are stacked such that the apexes of the non-circular first through holes of adjacent steel plate blocks are shifted from each other in the circumferential direction when viewed in the axial direction, and the shaft is fixed to the laminated core in a state in which the shaft has an outer circumferential surface in which the apexes of the non-circular shapes along corresponding steel plate blocks are shifted from each other in the circumferential direction by hydroforming, in which a liquid filled inside the shaft is pressurized and expanded .

In the rotor according to the first aspect of the present invention, as described above, the laminated core has a step skew structure in which the steel plate blocks are stacked such that the circumferential positions of the apexes of the non-circular first through holes of adjacent steel plate blocks are shifted from each other when viewed from the axial direction. The shaft is formed to conform to the inner circumferential surface of the first through hole of the laminated core by hydroforming, in which the liquid filled inside the shaft is pressurized and expanded, and is fixed to the laminated core. As a result, when viewed from the axial direction, the apex of the first through hole of one of the adjacent steel plate blocks is provided at the same position in the circumferential direction as the side between the apexes of the first through holes of the other of the adjacent steel plate blocks. Therefore, when viewed from the axial direction, the part of the shaft expanded by hydroforming to conform to the apex of the first through hole of the one steel plate block is provided so as to overlap the side of the other steel plate block. That is, the axial movement of the shaft is restricted by the other steel plate block at the part expanded to conform to the apex. In this case, the part that restricts the axial movement of the shaft is provided on the inside of the laminated core. This makes it possible to prevent the shaft from coming out of the laminated core while preventing the axial length of the rotor from increasing compared to when a stopper for the laminated core is provided on the axial outside of the laminated core.

A manufacturing method of a rotor in a second aspect of the present invention is a manufacturing method of a rotor including a laminated core in which a cylindrical shaft and a plurality of electromagnetic steel plates having a first through hole at the center through which the shaft is inserted are stacked, thereby forming a shaft insertion hole in which the shaft is disposed, by the first through hole, the manufacturing method including the steps of: forming a plurality of steel plate blocks formed of a plurality of electromagnetic steel plates stacked such that apexes of the first through holes having a non-circular shape when viewed in the axial direction of the laminated core overlap each other when viewed in the axial direction; forming a laminated core having a step-skew structure by stacking the plurality of steel plate blocks such that the circumferential positions of the apexes of the non-circular first through holes of adjacent steel plate blocks are shifted from each other when viewed in the axial direction; and forming an outer circumferential surface of the shaft in which the apexes of the non-circular shape along the inner circumferential surface of the first through hole of the laminated core are shifted from each other in the circumferential direction by hydroforming, in which a liquid filled inside the shaft is pressurized to expand the shaft, with the shaft inserted into the shaft insertion hole of the laminated core, thereby forming the outer circumferential surface of the shaft in which the circumferential positions of the apexes of the non-circular shape along the corresponding steel plate blocks are shifted from each other, and fixing the shaft to the laminated core.

In the rotor manufacturing method according to the second aspect of the present invention, as described above, the laminated core is formed such that the vertices of the non-circular first through holes of the adjacent steel plate blocks are offset from each other in the circumferential direction when viewed from the axial direction. In addition, the shaft is formed to conform to the inner circumferential surface of the first through hole of the laminated core by hydroforming, in which the liquid filled inside the shaft is pressurized and expanded, and is fixed to the laminated core. As a result, when viewed from the axial direction, the vertices of the first through holes of one of the adjacent steel plate blocks are provided at the same circumferential position as the side between the vertices of the first through holes of the other of the adjacent steel plate blocks. Therefore, when viewed from the axial direction, the part of the shaft expanded by hydroforming to conform to the vertices of the first through holes of the one steel plate block is provided so as to overlap with the side of the other steel plate block. That is, the axial movement of the shaft is restricted by the other steel plate block at the part expanded to conform to the vertex. In this case, the part that restricts the axial movement of the shaft is provided inside the laminated core. This makes it possible to provide a method for manufacturing a rotor that can prevent the shaft from coming out of the laminated core while preventing the axial length of the rotor from increasing compared to when a stopper for the laminated core is provided on the axial outside of the laminated core.

The present invention makes it possible to prevent the shaft from coming out of the laminated core in the axial direction while preventing the axial length of the rotor from increasing.

1 is a plan view showing a configuration of a rotor (rotating electric machine) according to an embodiment of the present invention; FIG. 2 is a partially enlarged view of the vicinity of a vertex of the electromagnetic steel sheet of FIG. 1 . 1 is a cross-sectional perspective view showing a configuration of a rotor core according to an embodiment of the present invention. FIG. 2 is a cross-sectional perspective view showing the configuration of a shaft according to the present embodiment. FIG. 2 is a cross-sectional perspective view showing the configuration of a laminated core according to the present embodiment. 4 is a cross-sectional view along the axial direction when viewed in the radial direction of the magnet insertion hole according to the present embodiment. FIG. FIG. 4 is a flow diagram showing a method for manufacturing a rotor according to the present embodiment. 4 is a cross-sectional view of a state in which a shaft according to the present embodiment is placed in a shaft insertion hole of a laminated core. FIG. 3 is a cross-sectional view of a laminated core and a shaft during hydroforming according to the present embodiment. FIG. FIG. 11 is a partially enlarged view of the vicinity of a vertex of an electromagnetic steel sheet according to a modified example of the present embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

[Present embodiment]
A rotor 1 and a method for manufacturing the rotor 1 according to the present embodiment will be described with reference to FIGS.

In this specification, "axial direction" means the direction along the rotation axis C of the rotor 1, which means the Z direction in the figure. Additionally, "radial direction" means the radial direction of the rotor 1 (R1 direction or R2 direction), and "circumferential direction" means the circumferential direction of the rotor 1 (E1 direction or E2 direction).

(Rotor Structure)
First, the structure of a rotor 1 according to the present embodiment will be described with reference to FIG.

As shown in FIG. 1, the rotating electric machine 100 includes a rotor 1 and a stator 2. The rotor 1 and the stator 2 are each formed in an annular shape. The rotor 1 is disposed facing the radially inner side of the stator 2. That is, in this embodiment, the rotating electric machine 100 is configured as an inner rotor type rotating electric machine. The rotor 1 (rotor core 4) includes a cylindrical shaft 3. The shaft 3 is disposed radially inner side of the rotor core 4. The shaft 3 is connected to an engine, an axle, or the like via a rotational force transmission member such as a gear. For example, the rotating electric machine 100 is configured as a motor, a generator, or a motor/generator, and is configured to be mounted on a vehicle.

The rotor 1 also includes a rotor core 4. The rotor core 4 includes a laminated core 4b in which multiple electromagnetic steel plates 4a (see FIG. 2) are laminated. The electromagnetic steel plates 4a are provided with a through hole 4c in the center, through which the shaft 3 is inserted. In the laminated core 4b, multiple electromagnetic steel plates 4a are laminated, and a shaft insertion hole 4d in which the shaft 3 is disposed is formed by the through hole 4c. In other words, the shaft insertion hole 4d is formed by providing multiple through holes 4c so that they are stacked on top of each other. The through hole 4c is an example of a "first through hole" in the claims.

Each of the electromagnetic steel sheets 4a includes a plurality of through holes 4g arranged circumferentially between the radially outer portion 4e of the electromagnetic steel sheet 4a and the radially inner portion 4f of the electromagnetic steel sheet 4a. A permanent magnet 5, which will be described later, is inserted into each of the plurality of through holes 4g. The laminated core 4b also includes a plurality of magnet insertion holes 4h formed by the plurality of through holes 4g arranged to overlap in the axial direction by stacking the plurality of electromagnetic steel sheets 4a. The through holes 4g are an example of a "second through hole" in the claims.

The rotor 1 also includes permanent magnets 5. The permanent magnets 5 are arranged in each of the multiple magnet insertion holes 4h. Multiple magnet insertion holes 4h (16 in this embodiment) are provided in the laminated core 4b.

The rotating electric machine 100 is configured as an interior permanent magnet motor (IPM motor). In addition, a pair of through holes 4g corresponding to one pole of the permanent magnet 5 is provided in a circumferential manner in the electromagnetic steel plate 4a in a plurality of pairs (eight in this embodiment). The pair of through holes 4g is arranged in a V-shape when viewed from the axial direction. The pair of through holes 4g is provided at equal angular intervals along the circumferential direction when viewed from the axial direction. However, the arrangement of the through holes 4g is not limited to this.

Each of the electromagnetic steel sheets 4a includes a bridge portion 4i (see FIG. 2) that is provided between adjacent through holes 4g and connects the radially outer portion 4e and the radially inner portion 4f. Specifically, the bridge portion 4i is provided between the through holes 4g that constitute a pair of through holes 4g.

The rotor core 4 rotates around the rotation axis C. The rotor core 4 is configured to rotate when the rotational force of the shaft 3 is transmitted to it.

The shaft 3 is also fixed to the laminated core 4b (rotor core 4) by hydroforming, in which the liquid 800 (see Figure 9) filled inside the shaft 3 is pressurized and expanded.

The stator 2 includes a stator core 2a and a coil 2b wound (placed) on the stator core 2a. The stator core 2a is placed radially outside the rotor core 4 (laminated core 4b). The stator core 2a is, for example, a plurality of electromagnetic steel sheets (silicon steel sheets) laminated in the axial direction, and is configured to be able to pass magnetic flux. The coil 2b is connected to an external power supply unit and is configured to be supplied with power (for example, three-phase AC power). The coil 2b is configured to generate a magnetic field when power is supplied. The rotor 1 and the shaft 3 are configured to rotate relative to the stator 2 when the engine or the like is driven, even if power is not supplied to the coil 2b. Although only a portion of the coil 2b is illustrated in FIG. 1, the coil 2b is placed around the entire circumference of the stator core 2a.

The permanent magnet 5 has a rectangular cross section perpendicular to the axial direction. For example, the permanent magnet 5 is configured so that the magnetization direction is in the short direction.

The rotor 1 also includes a resin material 6 that fills the magnet insertion hole 4h. The resin material 6 is provided to fix the permanent magnet 5 that is placed in the magnet insertion hole 4h.

In addition, each of the through holes 4c of the multiple electromagnetic steel sheets 4a has a polygonal shape when viewed from the axial direction (Z1 direction side). For example, the through holes 4c have a regular hexagonal shape when viewed from the axial direction.

In this embodiment, as shown in FIG. 2, the laminated core 4b has a skew structure in which the circumferential positions of the vertices 4j of the through holes 4c of at least some of the electromagnetic steel sheets 4a are offset from the circumferential positions of the vertices of the through holes 4c of the other electromagnetic steel sheets 4a (dashed lines in FIG. 2) when viewed from the axial direction. That is, in at least some of the electromagnetic steel sheets 4a, the vertices 4j of the through holes 4c of the electromagnetic steel sheets 4a adjacent in the axial direction are offset from each other in the circumferential direction.

As a result, between the electromagnetic steel sheets 4a whose vertices 4j are arranged with a circumferential offset, the vertices 4j are arranged radially outward of the side 4k connecting the vertices 4j when viewed from the axial direction. As a result, the corner 3c of the shaft 3 that expands to match the vertex 4j in one electromagnetic steel sheet 4a and the portion of the other electromagnetic steel sheet 4a near the side 4k whose vertex 4j is arranged with a circumferential offset from the one electromagnetic steel sheet 4a are arranged to overlap in the axial direction. Note that in FIG. 2, the electromagnetic steel sheet 4a whose vertex 4j is offset is shown by a dashed line.

The vertex 4j of the through hole 4c is the part corresponding to the intersection of adjacent sides 4k, and is not necessarily a pin angle, but may have a certain curvature. Also, the sides 4k are not necessarily straight, but may have a certain curvature.

In addition, in this embodiment, the amount of misalignment of the vertices 4j of the through holes 4c between axially adjacent steel plate blocks 40 in the circumferential direction is smaller than 1/2 of one side of the polygonal through hole 4c when viewed from the axial direction. Specifically, since the through holes 4c have a regular hexagonal shape, the angle of misalignment of the vertices 4j of the through holes 4c in the circumferential direction is smaller than 11.25 degrees (360÷16÷2).

As shown in Fig. 3, the shaft 3 is formed to conform to the inner circumferential surface 4l (see Fig. 2) of the through hole 4c of the laminated core 4b by hydroforming, in which the liquid filled inside the shaft 3 is pressurized and expanded, and is then fixed to the laminated core 4b. As a result, the outer circumferential surface 3a (see Fig. 4) of the shaft 3 is deformed to have the same shape as the inner circumferential surface 4m (see Fig. 5) of the shaft insertion hole 4d of the laminated core 4b.

As shown in FIG. 2, the outer peripheral surface 3a (inner peripheral surface 3b) of the shaft 3 expanded by hydroforming has a regular hexagonal shape in a cross section perpendicular to the axial direction, following the through hole 4c of the electromagnetic steel sheet 4a. As a result, unlike the case where the through hole 4c of the electromagnetic steel sheet 4a has a circular shape, the rotation of the shaft 3 relative to the laminated core 4b is restricted by the corners (vertices of a regular hexagon) of the outer peripheral surface 3a of the shaft 3. This makes it possible to more reliably prevent the shaft 3 from rotating in the circumferential direction relative to the laminated core 4b, compared to the case where the through hole 4c of the electromagnetic steel sheet 4a has a circular shape. Note that the through hole 4c of the electromagnetic steel sheet 4a may have a polygonal shape other than a regular hexagonal shape (for example, a regular 32-sided shape) when viewed from the axial direction.

As shown in FIG. 3, the laminated core 4b includes a plurality of (five in this embodiment) steel plate blocks 40 formed by stacking a plurality of electromagnetic steel plates 4a. In each of the plurality of steel plate blocks 40, the vertices 4j of the through holes 4c of the plurality of electromagnetic steel plates 4a overlap each other when viewed from the axial direction. In other words, in each of the plurality of steel plate blocks 40, the vertices 4j of the through holes 4c of the plurality of electromagnetic steel plates 4a are located at the same circumferential positions. In this embodiment, the laminated core 4b is formed by stacking five steel plate blocks 40.

Here, in this embodiment, the laminated core 4b has a step skew structure in which the steel plate blocks 40 are stacked such that the circumferential positions of the vertices 4j of the polygonal through holes 4c of adjacent steel plate blocks 40 are offset from each other when viewed from the axial direction. Specifically, the laminated core 4b is configured such that the circumferential positions of the vertices 4j of the through holes 4c of any of the multiple (five) steel plate blocks 40 are offset from each other when viewed from the axial direction. In particular, the offset amount (skew angle) between adjacent steel plate blocks 40 is approximately equal between any of the adjacent steel plate blocks 40.

As a result, in this embodiment, as shown in FIG. 6, each of the multiple magnet insertion holes 4h is formed along a direction inclined with respect to the axial direction so as to correspond to the skew angle between the multiple electromagnetic steel plates 4a (steel plate blocks 40) stacked in the laminated core 4b having a skew structure. Specifically, the magnet insertion holes 4h are configured by arranging the insertion holes 4n formed for each steel plate block 40 so as to be stacked. Each insertion hole 4n is provided along the axial direction. The magnet insertion holes 4h are provided along a direction inclined with respect to the axial direction by arranging the multiple insertion holes 4n in a stepped manner. Specifically, the magnet insertion holes 4h are formed in a V-shape. Note that the shape of the magnet insertion holes 4h is not limited to this, and may be configured to be inclined linearly, for example.

Note that FIG. 6 illustrates an example in which the permanent magnet 5 is composed of split magnets 5a arranged in each insertion hole 4n, but one permanent magnet 5 may be inserted into the magnet insertion hole 4h. In other words, one permanent magnet 5 may be provided so as to pass through five insertion holes 4n.

As shown in FIG. 2, in each of the multiple electromagnetic steel sheets 4a, the bridge portion 4i is arranged at a position that overlaps with the apex 4j of the through hole 4c in the circumferential direction when viewed from the axial direction. Specifically, each of all (eight) bridge portions 4i is arranged so as to overlap with the apex 4j of the through hole 4c in the circumferential direction when viewed from the axial direction.

In addition, in each of the multiple electromagnetic steel sheets 4a, each of the multiple (16) through holes 4g is arranged so as to overlap the side 4k of the through hole 4c in the circumferential direction when viewed from the axial direction. Here, when the shaft 3 expands by hydroforming, the shaft 3 first contacts the side 4k of the through hole 4c, and then expands so as to contact the apex 4j of the through hole 4c. As a result, the pressure applied to the part of the electromagnetic steel sheet 4a corresponding to the side 4k of the through hole 4c is greater than the pressure applied to the part corresponding to the apex 4j of the through hole 4c. Therefore, when hydroforming is performed before inserting the permanent magnet 5 into the through hole 4g, the gap in the through hole 4g (magnet insertion hole 4h) can effectively absorb the hydroforming pressure applied to the part corresponding to the side 4k of the through hole 4c.

As shown in FIG. 3, the rotor 1 is provided with an oil injection section 7 that is inserted into the shaft 3 when the shaft 3 is placed in the shaft insertion hole 4d (see FIG. 1). The tip 7a of the oil injection section 7 is located in the axial center of the shaft 3. The tip 7a of the oil injection section 7 is provided with an injection port 7b that injects (sprays) cooling oil.

The shaft 3 also includes an oil discharge hole 3d for discharging the cooling oil circulating inside the shaft 3 to the outside of the shaft 3. The oil discharge hole 3d is provided on both the Z1 side and the Z2 side. The oil discharge hole 3d is also provided on the outside of the laminated core 4b in the axial direction.

In this embodiment, the oil injection unit 7 is configured to inject cooling oil toward the inner circumferential surface 3b of the shaft 3 inserted into the shaft insertion hole 4d of the laminated core 4b having a skew structure. That is, the cooling oil injected from the oil injection unit 7 flows along the inner circumferential surface 3b of the shaft 3 formed (deformed) in a skew shape. As a result, the cooling oil flows in a spiral along the inner circumferential surface 3b of the shaft 3 from the center of the shaft 3 toward the end side, and is finally discharged to the outside of the shaft 3 from the oil discharge hole 3d. While flowing in a spiral shape inside the shaft 3, the cooling oil cools the laminated core 4b via the shaft 3.

(Rotor manufacturing method)
Next, a method for manufacturing the rotor 1 will be described with reference to FIGS.

First, as shown in FIG. 7, in step S1, a process of forming a plurality of steel plate blocks 40 (see FIG. 3) is carried out. Specifically, each of the plurality of steel plate blocks 40 is formed by stacking a plurality of electromagnetic steel plates 4a such that the vertices 4j of the polygonal through holes 4c (see FIG. 2) overlap each other when viewed from the axial direction. Also, in step S1, a split magnet 5a is placed in each of the plurality of insertion holes 4n in each of the plurality of steel plate blocks 40.

Next, in step S2, a process of forming the laminated core 4b is performed. Specifically, a laminated core 4b having a skew structure (see FIG. 2) is formed in which the circumferential positions of the vertices 4j of the polygonal through holes 4c of at least some of the electromagnetic steel sheets 4a are offset from the circumferential positions of the vertices 4j of the polygonal through holes 4c of the other electromagnetic steel sheets 4a. In detail, in the process of forming the laminated core 4b in step S2, the laminated core 4b having a step skew structure is formed by stacking the multiple steel plate blocks 40 so that the circumferential positions of the vertices 4j of the polygonal through holes 4c of adjacent steel plate blocks 40 are offset from each other when viewed from the axial direction.

Next, in step S3, as shown in FIG. 8, a process of placing the shaft 3 in the laminated core 4b is performed. Specifically, the shaft 3 is inserted in the axial direction (Z direction) into the shaft insertion hole 4d of the laminated core 4b.

Then, in step S4, with the shaft 3 inserted into the shaft insertion hole 4d of the laminated core 4b, the shaft 3 is formed by hydroforming so as to conform to the inner circumferential surface 4l (see FIG. 2) of the through hole 4c of the laminated core 4b, and is fixed to the laminated core 4b.

Specifically, as shown in FIG. 9, the shaft 3 is placed in the shaft insertion hole 4d of the laminated core 4b, and hydroforming is performed by pressurizing the liquid 800 filled inside the shaft 3. At this time, the laminated core 4b and the shaft 3 are placed (set) in the hydroforming machine 900.

This hydroforming causes the shaft 3 to expand to conform to the inner circumferential surface 4m of the shaft insertion hole 4d of the laminated core 4b (the inner circumferential surface 4l of the through hole 4c of the electromagnetic steel plate 4a). As a result, between the electromagnetic steel plates 4a (steel plate blocks 40) (see FIG. 2) whose vertices 4j are arranged offset from each other in the circumferential direction, the corner portion 3c of the shaft 3 that has expanded to conform to the vertex 4j of one electromagnetic steel plate 4a (steel plate block 40) and the portion near the side 4k of the other electromagnetic steel plate 4a (steel plate block 40) whose vertices 4j are offset from each other are arranged to overlap in the axial direction.

The hydroforming machine 900 also includes an upper die 901 that presses the laminated core 4b from the Z1 side, and a lower die 902 that presses the laminated core 4b from the Z2 side. The hydroforming machine 900 also includes a regulating unit 903 that regulates the radial movement of the laminated core 4b from the radial outside.

The hydroforming machine 900 also includes an upper seal portion 904 that seals the end of the shaft 3 on the Z1 side, and a lower seal portion 905 that seals the end of the shaft 3 on the Z2 side. The upper seal portion 904 and the lower seal portion 905 are provided with introduction paths 904a and 905a, respectively, for introducing liquid 800 into the inside of the shaft 3.

After hydroforming is completed, the rotor 1 is released from the hydroforming machine 900. Even after the rotor 1 is released from the hydroforming machine 900, the laminated core 4b and the shaft 3 remain fixed together.

[Effects of this embodiment]
In this embodiment, the following effects can be obtained.

(Rotor effect)
In this embodiment, as described above, the laminated core (4b) includes a plurality of steel plate blocks (40) made of a plurality of electromagnetic steel plates (4a) stacked such that the vertices (4j) of the first through holes (4c) of a non-circular shape overlap each other when viewed from the axial direction, and has a step-skew structure in which the steel plate blocks (40) are stacked such that the vertices (4j) of the first through holes (4c) of the non-circular shape of the adjacent steel plate blocks (40) are shifted from each other in the circumferential direction when viewed from the axial direction. In addition, the shaft (3) is formed to conform to the inner circumferential surface (4l) of the first through hole (4c) of the laminated core (4b) by hydroforming in which the liquid (800) filled inside the shaft (3) is pressurized and expanded, and is fixed to the laminated core (4b). As a result, when viewed from the axial direction, the apex (4j) of the first through hole (4c) of one of the adjacent steel plate blocks (40) is provided at the same position in the circumferential direction as the side (4k) between the apexes (4j) of the first through holes (4c) of the other of the adjacent steel plate blocks (40). Therefore, when viewed from the axial direction, the portion (corner (3c)) of the shaft (3) expanded by hydroforming that is expanded to match the apex (4j) of the first through hole (4c) of the one steel plate block (40) is provided to overlap the side (4k) of the other steel plate block (40). That is, the axial movement of the shaft (3) is restricted by the other steel plate block (40) at the portion (corner (3c)) that is expanded to match the apex (4j). In this case, the portion that restricts the axial movement of the shaft (3) is provided inside the laminated core (4b). This makes it possible to prevent the shaft (3) from coming off the laminated core (4b) while preventing the axial length of the rotor (1) from increasing compared to the case where a stopper for the laminated core (4b) is provided on the axial outside of the laminated core (4b).

In addition, in this embodiment, as described above, the first through holes (4c) of each of the multiple electromagnetic steel plates (4a) have a regular polygonal shape when viewed from the axial direction. Furthermore, the amount of deviation in the circumferential position of the vertices (4j) of the first through holes (4c) of the steel plate blocks (40) adjacent in the axial direction is smaller than 1/2 of one side of the regular polygonal first through hole (4c) when viewed from the axial direction. With this configuration, when the shaft (3) expands by hydroforming, the parts (corners (3c)) that are relatively close to each other when viewed from the axial direction can be expanded, compared to when the deviation is 1/2 or more of one side of the first through hole (4c). As a result, the relatively close parts can be deformed to follow each other. This makes it possible to easily expand the shaft (3) by hydroforming at a relatively low pressure.

In addition, in this embodiment, as described above, the rotor (1) includes an oil injection section (7) that is inserted into the inside of the shaft (3) when the shaft (3) is disposed in the shaft insertion hole (4d). The oil injection section (7) is configured to inject cooling oil toward the inner circumferential surface (3b) of the shaft (3) inserted into the shaft insertion hole (4d) of the laminated core (4b) having a skew structure. Here, the cooling oil is likely to accumulate in the corners of the inner circumferential surface (3b) of the shaft (3) that are formed by expanding to match the apex (4j) of the first through hole (4c). Therefore, since the laminated core (4b) has a skew structure, the inner circumferential surface (3b) of the shaft (3) is also formed in a skew shape, and as viewed from the axial direction, there are portions where the circumferential positions of the above-mentioned corners are shifted between adjacent electromagnetic steel plates (4a). As a result, as the shaft (3) rotates, the cooling oil flows to move between the corners that are offset in the circumferential direction as described above (moving relative to the shaft (3)). As a result, unlike when the cooling oil accumulates in the corners and does not move relative to the shaft (3), the cooling oil that accumulates in the corners does not rotate together with the shaft (3), so energy loss can be reduced by the amount of energy required to rotate the cooling oil.

In this embodiment, as described above, the rotor (1) includes a permanent magnet (5). Each of the plurality of electromagnetic steel sheets (4a) includes a plurality of second through holes (4g) into which the permanent magnet (5) is inserted and which are arranged circumferentially between the radial outer portion (4e) of the electromagnetic steel sheet (4a) and the radial inner portion (4f) of the electromagnetic steel sheet (4a), and a bridge portion (4i) provided between adjacent second through holes (4g) and connecting the radial outer portion (4e) and the radial inner portion (4f). In each of the plurality of electromagnetic steel sheets (4a), the bridge portion (4i) is arranged at a position that overlaps with the apex (4j) of the first through hole (4c) in the circumferential direction when viewed from the axial direction. Here, when the shaft (3) expands in the polygonal first through hole (4c), the shaft (3) first comes into contact with the side (4k) of the first through hole (4c), and then the shaft (3) expands to follow the part corresponding to the apex (4j) of the first through hole (4c). That is, the stress caused by the expansion of the shaft (3) is smaller at the apex (4j) of the first through hole (4c) than at the side (4k) of the first through hole (4c). Therefore, by arranging the bridge portion (4i) at a position overlapping with the apex (4j) of the first through hole (4c) in the circumferential direction, the stress applied to the bridge portion (4i) due to the expansion of the shaft (3) can be made relatively small. As a result, the residual stress remaining in the bridge portion (4i) can be reduced, and therefore the bridge portion (4i) can be prevented from breaking due to the residual stress when the rotor (1) rotates.

(Effects of rotor manufacturing method)
In the present embodiment, as described above, the manufacturing method of the rotor (1) includes a step of forming a plurality of steel plate blocks (40) made of a plurality of electromagnetic steel plates (4a) stacked such that the vertices (4j) of the first through holes (4c) having a non-circular shape as viewed in the axial direction of the laminated core (4b) overlap each other as viewed in the axial direction. The manufacturing method of the rotor (1) also includes a step of forming a laminated core (4b) having a step-skew structure by stacking the plurality of steel plate blocks (40) such that the circumferential positions of the vertices of the non-circular first through holes (4c) of adjacent steel plate blocks (40) are shifted from each other as viewed in the axial direction. The manufacturing method of the rotor (1) also includes a step of forming the shaft (3) so as to conform to the inner peripheral surface (4l) of the first through hole (4c) of the laminated core (4b) and fixing the shaft (3) to the laminated core (4b) by hydroforming, in which the liquid filled inside the shaft (3) is pressurized to expand the shaft (3) while the shaft (3) is inserted into the shaft insertion hole (4d) of the laminated core (4b). As a result, when viewed from the axial direction, the apex (4j) of the first through hole (4c) of one of the adjacent steel plate blocks (40) is located at the same position in the circumferential direction as the side (4k) between the apexes (4j) of the first through holes (4c) of the other of the adjacent steel plate blocks (40). Therefore, when viewed from the axial direction, the portion (corner portion (3c)) of the shaft (3) expanded by hydroforming so as to follow the apex (4j) of the first through hole (4c) of the one steel plate block (40) is provided so as to overlap with the side (4k) of the other steel plate block (40). That is, the axial movement of the shaft (3) is restricted by the other steel plate block (40) at the portion expanded so as to follow the apex (4j). In this case, the portion restricting the axial movement of the shaft (3) is provided on the inside of the laminated core (4b). This makes it possible to provide a manufacturing method for a rotor (1) that can prevent the shaft (3) from coming off the laminated core (4b) while preventing the axial length of the rotor (1) from increasing compared to a case in which a stopper for the laminated core (4b) is provided on the axial outside of the laminated core (4b).

[Modification]
It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and further includes all modifications (variations) within the meaning and scope of the claims.

For example, in the above embodiment, an example was shown in which the through hole 4c (first through hole) has a regular polygonal shape, but the present invention is not limited to this. For example, the through hole 4c (first through hole) may have a polygonal shape that is not a regular polygonal shape. Furthermore, the through hole 4c (first through hole) may have a shape other than a polygonal shape and have vertices.

In addition, in the above embodiment, an example in which five steel plate blocks 40 are provided is shown, but the present invention is not limited to this. There may be two or more steel plate blocks 40.

In addition, in the above embodiment, an example was shown in which the amount of deviation in the circumferential position of the vertices 4j of the through holes 4c (first through holes) of the steel plate blocks 40 adjacent in the axial direction is smaller than 1/2 of one side of the through hole 4c when viewed from the axial direction, but the present invention is not limited to this. The amount of deviation may be larger than 1/2 as long as it is not an integer multiple of one side of the through hole 4c when viewed from the axial direction.

In the above embodiment, the magnet insertion holes 4h are formed in a stepped shape, but the present invention is not limited to this. The magnet insertion holes 4h may be linearly inclined with respect to the axial direction. The magnet insertion holes 4h may also be formed linearly so as to extend along the axial direction. In these cases, the permanent magnet 5 placed in one magnet insertion hole 4h is formed integrally without being divided.

In the above embodiment, the laminated core 4b is formed by stacking the steel plate blocks 40 in which the split magnets 5a are arranged in the insertion holes 4n, but the present invention is not limited to this. For example, after inserting one permanent magnet 5 into the magnet insertion hole 4h in a state where multiple steel plate blocks 40 are stacked, the steel plate blocks 40 may be shifted (skewed) in the circumferential direction. In this case, by skewing the steel plate blocks 40 with a thermosetting adhesive or the like pre-applied in the magnet insertion hole 4h, the permanent magnet 5 is skewed in a state where it is covered with the thermosetting adhesive or the like, which is a soft material before hardening, so that it is possible to prevent the permanent magnet 5 from being damaged.

In addition, in the above embodiment, an example was shown in which the bridge portion 4i of each of the multiple electromagnetic steel sheets 4a is arranged at a position that overlaps with the apex 4j of the through hole 4c (first through hole) in the radial direction when viewed from the axial direction, but the present invention is not limited to this. In each of the multiple electromagnetic steel sheets 4a, the bridge portion 4i does not have to overlap with the apex 4j in the radial direction when viewed from the axial direction.

Specifically, as shown in FIG. 10, in each of the multiple electromagnetic steel sheets 4a, the side 4k of the through hole 4c (first through hole) is arranged at a position overlapping the d-axis of the laminated core 4b in the circumferential direction when viewed from the axial direction. In the example shown in FIG. 10, the d-axis extends in a direction from the rotation axis C of the laminated core 4b toward the bridge portion 4i. That is, in the example shown in FIG. 10, the side 4k of the through hole 4c is arranged at a position overlapping the bridge portion 4i in the circumferential direction when viewed from the axial direction. Here, the circumferential position where the side 4k of the through hole 4c is provided has a larger radial width of the laminated core 4b (electromagnetic steel sheet 4a) than the circumferential position where the apex 4j of the through hole 4c is provided when viewed from the axial direction. Therefore, by arranging the side 4k of the through hole 4c at a position overlapping the d-axis of the laminated core 4b in the circumferential direction, the magnetic flux passes through the part of the laminated core 4b with a larger radial width. As a result, it is possible to prevent the motor output from decreasing due to a decrease in magnetic flux.

In the above embodiment, the positions of the through holes 4c (first through holes) in the circumferential direction are shifted from each other in any of the five adjacent steel plate blocks 40, but the present invention is not limited to this. The positions of the through holes 4c in the circumferential direction may be shifted from each other only in some of the adjacent steel plate blocks 40.

1 rotor 3 shaft 3b inner peripheral surface (inner peripheral surface of shaft)
4a: electromagnetic steel sheet; 4b: laminated core; 4c: through hole (first through hole);
4d Shaft insertion hole 4e Radial outer portion 4f Radial inner portion 4g Through hole (second through hole)
4i Bridge portion 4j Vertex 4l Inner peripheral surface (inner peripheral surface of first through hole)
5 permanent magnet 7 oil injection part 40 steel plate block 800 liquid

Claims (5)

A cylindrical shaft;
a laminated core in which a shaft insertion hole in which the shaft is disposed is formed by laminating a plurality of electromagnetic steel plates having a first through hole at the center thereof, the first through hole being formed by the laminated electromagnetic steel plates,
the first through hole of each of the plurality of electromagnetic steel sheets has a non-circular shape when viewed in an axial direction of the laminated core,
the laminated core includes a plurality of steel plate blocks formed of a plurality of the electromagnetic steel plates stacked such that vertices of the non-circular first through holes overlap each other as viewed from the axial direction, and has a step-skew structure in which the steel plate blocks are stacked such that positions of the vertices of the non-circular first through holes of adjacent steel plate blocks in the circumferential direction are shifted from each other as viewed from the axial direction,
The shaft is formed into a non-circular shape that conforms to the inner surface of the first through hole of the laminated core by hydroforming, in which a liquid filled inside the shaft is pressurized and expanded , and the shaft is fixed to the laminated core with an outer peripheral surface in which the apexes of the non-circular shape along the corresponding steel plate blocks are offset from each other in the circumferential direction . the first through hole of each of the plurality of electromagnetic steel plates has a regular polygonal shape when viewed in the axial direction,
2. The rotor according to claim 1, wherein a circumferential positional deviation of vertices of the first through holes of the steel plate blocks adjacent in the axial direction is smaller than 1/2 of one side of the regular polygon-shaped first through hole when viewed in the axial direction. The oil injection part is inserted into the shaft when the shaft is disposed in the shaft insertion hole.
3. The rotor according to claim 1, wherein the oil injection portion is configured to inject cooling oil toward an inner peripheral surface of the shaft inserted into the shaft insertion hole of the laminated core having a skew structure. Further comprising a permanent magnet;
Each of the plurality of electromagnetic steel sheets has a plurality of second through holes into which the permanent magnets are inserted and which are circumferentially arranged between a radially outer portion of the electromagnetic steel sheet and a radially inner portion of the electromagnetic steel sheet;
a bridge portion provided between adjacent second through holes and connecting the radially outer portion and the radially inner portion,
A rotor according to any one of claims 1 to 3, wherein in each of the plurality of electromagnetic steel plates, the bridge portion is arranged at a position that circumferentially overlaps with a vertex of the first through hole when viewed from the axial direction. 1. A method for manufacturing a rotor comprising: a laminated core including a cylindrical shaft and a plurality of electromagnetic steel plates having a first through hole at a center thereof, the first through hole defining a shaft insertion hole in which the shaft is disposed, the laminated core being formed by laminating the plurality of electromagnetic steel plates, the first through hole defining the shaft insertion hole,
forming a plurality of steel plate blocks constituted by a plurality of the electromagnetic steel plates laminated such that vertices of the first through holes, which have a non-circular shape as viewed in an axial direction of the laminated core, overlap each other as viewed in the axial direction;
forming the laminated core having a step-skew structure by stacking the plurality of steel plate blocks such that, as viewed in the axial direction, vertices of the non-circular first through holes of adjacent steel plate blocks are shifted from each other in the circumferential direction;
and forming the shaft into a non-circular shape that conforms to the inner surface of the first through hole of the laminated core by hydroforming, in which the shaft is inserted into the shaft insertion hole of the laminated core and the liquid filled inside the shaft is pressurized to expand the shaft, thereby forming the outer peripheral surface of the shaft in which the apexes of the non-circular shape are offset from each other in the circumferential direction along the corresponding steel plate blocks, and fixing the shaft to the laminated core.

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