Integrated forged rotor, method for manufacturing integrated forged rotor, and forging die

Abstract

To provide a forged integrated rotor capable of reducing the number of components and man-hours and improving mechanical strength and rotation balance in a motor.SOLUTION: The forged integrated rotor 3 for a motor comprises a rotor core 10 having a protrusion 21 and a recess 22 on the outer circumferential side, and a shaft 11 integrated coaxially with the rotor core 10. The shaft 11 preferably comprises a flange-like portion 30 in which a balancing hole 31 can be formed. Such a forged integrated rotor 3 is obtained by performing a hot forging step of forming the rotor core 10 having the convex portion 21 and the concave portion 22 on the outer peripheral side and the shaft 11 coaxially integrated with the rotor core 10 by hot forging a metal material, and a machining step of performing machining on at least one of the rotor core 10 and the shaft 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a forged integral rotor for a motor, a method for manufacturing the forged integral rotor, and a forging die used for manufacturing the forged integral rotor. [Background technology]

[0002] Conventionally, in a typical motor, the rotor is mainly composed of a rotor core, a shaft, and a ring (nut) (see Patent Document 1).

[0003] In the rotor disclosed in Patent Document 1, the rotor core is made of laminated disk-shaped electromagnetic steel plates each having a circular hole in the center, and is formed into a cylindrical shape with a hollow portion opened axially in the lamination direction. The shaft has a shaft body that can be inserted through the hollow portion of the rotor core and a flange formed at a predetermined position in the axial direction on the shaft body, and is configured so that a ring can be screwed onto the shaft body at a position spaced a predetermined distance from the flange.

[0004] A rotor of this configuration is assembled by inserting the shaft body into the hollow portion of the rotor core so that the flange on the shaft abuts against one axial end face of the rotor core, then screwing a ring onto the shaft body so as to sandwich the rotor core between the flange and the shaft body, and tightening the ring. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-93225 Summary of the Invention [Problem to be solved by the invention]

[0006] In an assembled rotor such as that described in Patent Document 1, the rotor core, shaft, and ring must be individually manufactured and then assembled as described above, which is time-consuming. In particular, the rotor core is made of multiple laminated electromagnetic steel sheets, which requires a large number of parts and increases the number of steps. Furthermore, in order to improve the mechanical strength and rotational balance of the rotor, the individually manufactured rotor core, shaft, and ring must be assembled with high precision, which makes it difficult to achieve the desired improvements in mechanical strength and rotational balance due to the need to balance this with production efficiency.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a forged integral rotor, a method for manufacturing a forged integral rotor, and a forging die that can reduce the number of parts and labor required in a motor and improve the mechanical strength and rotational balance. [Means for solving the problem]

[0008] The characteristic configuration of the forged integral rotor according to the present invention for solving the above problems is as follows: A forged integral rotor for a motor, a rotor core having a protrusion and a recess on an outer periphery thereof; a shaft that is coaxially integrated with the rotor core; The purpose is to provide the following.

[0009] With the forged one-piece rotor of this configuration, the rotor core and shaft are integrated by forging, which not only eliminates the ring (nut) that was previously required, but also reduces the number of parts and labor required compared to conventional assembled rotors in which the rotor core, shaft, and ring are manufactured separately and then assembled, and also improves mechanical strength and rotational balance.

[0010] In the forged integral rotor according to the present invention, The shaft preferably includes a flange-like portion in which a balance hole can be formed.

[0011] According to the forged rotor of this configuration, by forming balance holes in the flange-shaped portion, it is possible to correct the mass imbalance with respect to the center of rotation of the forged rotor, thereby eliminating the mass imbalance and further improving the rotational balance, thereby suppressing vibration during rotation and enabling smooth rotation.

[0012] Next, the characteristic configuration of the manufacturing method of the forged integral rotor according to the present invention for solving the above problems is as follows: A method for manufacturing a forged integral rotor for a motor, comprising: The method includes a hot forging step of hot forging a metal material to form a rotor core having protrusions and recesses on its outer periphery, and a shaft that is integrated and coaxial with the rotor core.

[0013] According to the manufacturing method of the integrally forged rotor of this configuration, a hot forging process can be performed to obtain an integrally forged rotor for a motor, which includes a rotor core having protrusions and recesses on its outer periphery and a shaft that is integrated and coaxial with the rotor core. The integrally forged rotor obtained in this manner can reduce the number of parts and labor required, and can also improve mechanical strength and rotational balance, compared to conventional assembled rotors.

[0014] In the method for manufacturing a forged integral rotor according to the present invention, It is preferable that the manufacturing method further includes a machining step of machining at least one of the rotor core and the shaft.

[0015] In a motor, an air gap exists between the rotor core and the stator. It is desirable that this air gap be small and uniform around the entire circumference as long as the rotor core and the stator do not mechanically contact each other. Furthermore, the portion of the shaft supported by the bearing requires dimensional accuracy to ensure a shaft diameter that allows the bearing to be properly fitted. According to the manufacturing method of the forged rotor of this configuration, the air gap can be made small and uniform around the entire circumference by machining the convex portion on the outer periphery of the rotor core. By reducing the air gap, the magnetic field between the forged rotor and the stator becomes stronger, improving the density of the power that can be transmitted. Furthermore, by making the air gap uniform around the entire circumference, changes in magnetic flux in the air gap can be suppressed, allowing current to flow balanced. Furthermore, according to the manufacturing method of the forged rotor of this configuration, by machining the portion of the shaft supported by the bearing, the shaft diameter can be made within the dimensional tolerance required for a shaft that allows the bearing to be properly fitted.

[0016] Next, the characteristic configuration of the forging die according to the present invention for solving the above problems is as follows: A forging die having an upper die and a lower die for manufacturing a forged integral rotor for a motor, The cavity formed by the upper mold and the lower mold is a rotor core forming section for forming a rotor core having a protrusion and a recess on an outer circumferential side; a shaft forming portion for forming a shaft that is coaxial with and integrated with the rotor core; The purpose is to have.

[0017] With the forging die of this configuration, hot forging of a metal material forms a rotor core having protrusions and recesses on its outer periphery in the rotor core forming section, and forms a shaft coaxially integrated with the rotor core in the shaft forming section. In this way, a forged integral rotor for a motor can be obtained, including a rotor core having protrusions and recesses on its outer periphery and a shaft coaxially integrated with the rotor core. The forged integral rotor obtained in this way can reduce the number of parts and labor required and can achieve improved mechanical strength and rotational balance compared to conventional assembled rotors. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic structural explanatory diagram of a reluctance motor equipped with a forged integral rotor according to one embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory view of a forging die for manufacturing a forged integral rotor according to one embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing the steps of a manufacturing process for a forged integral rotor according to one embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory diagram of a manufacturing process of a forged integral rotor according to one embodiment of the present invention. [Figure 5] FIG. 5 is a comparative explanatory view of a forged integral rotor according to one embodiment of the present invention before and after machining. [Figure 6] FIG. 6 is an explanatory diagram of a forged integral rotor according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described below with reference to the drawings. In the following embodiments, the present invention will be described by taking as an example a case where the present invention is applied to a rotor for a reluctance motor. However, the present invention is not intended to be limited to the configurations shown in the following embodiments and drawings. In this specification, when a rotating body (forged integral rotor 3) rotates around a virtual center line, the virtual center line is referred to as an axis AL, and the direction in which the axis line AL extends is referred to as an axial direction. In the following, the terms "vertical direction (up-down direction)" and "axial direction" will be used appropriately to specify directions depending on the component being described, but the vertical direction and the axial direction are identical unless otherwise specified.

[0020] <Schematic configuration of a reluctance motor> FIG. 1 is a schematic structural explanatory diagram of a reluctance motor 1 equipped with a forged integral rotor 3 according to one embodiment of the present invention. FIG. 1(a) is a plan view, and FIG. 1(b) is a side view. As shown in FIGS. 1(a) and 1(b), the reluctance motor 1 is equipped with a stator 2 in which a plurality of coils 2a are arranged at a predetermined angular pitch in the circumferential direction, and a forged integral rotor 3 incorporated inside the stator 2. Note that, although this embodiment illustrates a case in which the rotor 3 has four poles and the stator 2 has six slots, the numbers of poles and slots are not particularly limited.

[0021] <Forged one-piece rotor> As shown in FIG. 1(b), the forged integral rotor 3 includes a rotor core 10 that can rotate about an axis AL, and a shaft 11 that is coaxially integrated with the rotor core 10. Here, "integrated" refers to a state in which the crystalline structure of the metal material M, which will be described later, is compressed and bent through a crushing process and a hot forging process, which will be described later, to form continuous metal flow lines that extend from a first shaft portion 11a, through the rotor core 10, to a second shaft portion 11b, which will be described later, so as to conform to the shape of the forged integral rotor 3 as a finished product, as shown in FIG. 5. Therefore, this does not include a state in which the above-described grain flows are not formed, such as when the first shaft portion 11a, the rotor core 10, and the second shaft portion 11b are manufactured separately and then integrated by fastening them together with fastening means such as bolts, or when they are integrated by welding.

[0022] <Rotor core> The rotor core 10 has a cylindrical portion 20 extending cylindrically in the axial direction, a plurality of (four in this example) protruding portions 21 protruding radially outward from the cylindrical portion 20 at a predetermined angular pitch in the circumferential direction of the cylindrical portion 20, and a plurality of (four in this example) recessed portions 22 formed between adjacent protruding portions 21.

[0023] <Shaft> The shaft 11 has a first shaft portion 11a that extends axially along the axis AL on one axial side of the rotor core 10 (the upper side in FIG. 1(b)), and a second shaft portion 11b that extends axially along the axis AL on the other axial side of the rotor core 10 (the lower side in FIG. 1(b)). In the reluctance motor 1, the shaft 11 is supported at both ends by bearings (not shown). A first bearing fitting portion 25, into which one bearing is fitted, is formed at a predetermined axial portion of the first shaft portion 11a. Similarly, a second bearing fitting portion 26, into which the other bearing is fitted, is formed at a predetermined axial portion of the second shaft portion 11b.

[0024] <Flange-shaped part> The shaft 11 includes a flange-like portion 30 in which a balance hole 31 can be formed. The flange-like portion 30 is located between the rotor core 10 and the first bearing fitting portion 25 and is integrally formed coaxially with the rotor core 10 and the first shaft portion 11a in a form that protrudes in an annular shape from the rotor core 10 toward one axial side (the upper side in FIG. 1(b)) from the rotor core 10.

[0025] The reluctance motor 1 is configured to rotate the forged integral rotor 3 by utilizing the reluctance torque generated by the difference in magnetic resistance between the protrusions 21, which have a relatively small magnetic resistance relative to the stator 2, and the recesses 22, which have a relatively large magnetic resistance relative to the stator 2.

[0026] Fig. 2 is an explanatory diagram of a forging die for manufacturing a forged integral rotor 3 according to one embodiment of the present invention. Fig. 2(a) is a vertical cross-sectional end view of a first forging die 40 used in the crushing process. Fig. 2(b) is a vertical cross-sectional end view and a cross-sectional end view of a main part of a second forging die 50 used in the rough forming process. Fig. 2(c) is a vertical cross-sectional end view and a cross-sectional end view of a main part of a third forging die 60 used in the finish forming process.

[0027] The first forging die 40 shown in FIG. 2( a) includes an upper die 41 and a lower die 42 arranged vertically opposite each other. The upper die 41 is set on a slide of a press machine (not shown), and the lower die 42 is set on a bolster of the same press machine (the same applies to the second forging die 50 and the third forging die 60). The upper die 41 is formed with a generally truncated cone-shaped recess 43. The generally truncated cone-shaped recess 43 is formed with a recessed shape such that the inner diameter gradually decreases toward the top in order to form the upper end of a cylindrical metal material M (described later) as a workpiece into a tapered shape suitable for centering. The lower die 42 is formed with a generally inverted truncated cone-shaped recess 44 corresponding to the generally truncated cone-shaped recess 43. The generally inverted truncated cone-shaped recess 44 is formed with a recessed shape such that the inner diameter gradually decreases toward the bottom in order to form the lower end of the metal material M into a tapered shape suitable for centering. In the first forging die 40, the metal material M is placed between the approximately truncated cone-shaped recess 43 in the upper die 41 and the approximately inverted truncated cone-shaped recess 44 in the lower die 42, and by operating a press machine to lower the upper die 41 relative to the lower die 42, both ends of the metal material M can be formed into a tapered shape suitable for centering.

[0028] 2(b) includes an upper die 51 and a lower die 52 arranged opposite to each other in the vertical direction. A cavity 53 formed by the upper die 51 and the lower die 52 has a pre-rotor core forming portion 54 and a pre-shaft forming portion 55.

[0029] The pre-rotor core forming section 54 is used to form a pre-rotor core 210, which is a pre-stage that will eventually become the rotor core 10, from a workpiece (a first intermediate material 100, which will be described later) whose both ends have been formed into a tapered shape by the first forging die 40. The pre-rotor core forming section 54 includes a pre-cylindrical portion forming section 54a for forming a pre-cylindrical portion 220, which is a pre-stage that will eventually become the cylindrical portion 20, a pre-protrusion forming section 54b for forming a pre-protrusion 221, which is a pre-stage that will eventually become the protrusion 21, and a pre-recess forming section 54c for forming a pre-recess 222, which is a pre-stage that will eventually become the recess 22.

[0030] The pre-shaft forming section 55 is used to form a pre-shaft 211 (described later) from the first intermediate material 100, which is a preliminary stage that will eventually become the shaft 11. The pre-shaft forming section 55 includes a pre-first shaft portion forming section 55a for forming a pre-first shaft portion 211a (described later) which is a preliminary stage that will eventually become the first shaft portion 11a, and a pre-second shaft portion forming section 55b for forming a pre-second shaft portion 211b (described later) which is a preliminary stage that will eventually become the second shaft portion 11b.

[0031] 2(c) includes an upper die 61 and a lower die 62 arranged opposite to each other in the vertical direction. A cavity 63 formed by the upper die 61 and the lower die 62 has a rotor core forming portion 64, a shaft forming portion 65, and a flange-shaped portion forming portion 66.

[0032] The rotor core forming section 64 is used to form the rotor core 10 before machining from the workpiece (second intermediate material 200, described later) that has been roughly formed by the second forging die 50. The rotor core forming section 64 includes a columnar portion forming section 64a for forming the columnar portion 20 before machining, a convex portion forming section 64b for forming the convex portion 21 before machining, and a recessed portion forming section 64c for essentially forming the recessed portion 22 without performing machining, as described later.

[0033] The shaft forming section 65 is for forming the shaft 11 before machining from the second intermediate material 200. The shaft forming section 65 includes a first shaft portion forming section 65a for forming the first shaft portion 11a before machining, and a second shaft portion forming section 65b for forming the second shaft portion 11b before machining.

[0034] The flange-shaped portion forming portion 66 is for forming the flange-shaped portion 30 on the second intermediate material 200 before machining.

[0035] Fig. 3 is a flowchart showing the procedure of the manufacturing process of the forged rotor 3 according to one embodiment of the present invention. Fig. 4 is an explanatory diagram of the manufacturing process of the forged rotor 3 according to one embodiment of the present invention. Fig. 5 is an explanatory diagram comparing the forged rotor 3 according to one embodiment of the present invention before and after machining. The manufacturing method of the forged rotor 3 will be explained using Figs. 3 to 5. In Fig. 3, the symbol "S" represents a step.

[0036] <Heating process: Step S1> First, as shown in step S1 of Fig. 3 and Fig. 4(a), a workpiece (metal material M) is heated to approximately 1200°C using an induction heating furnace (not shown). In this example, a cylindrical steel material is used as the metal material M.

[0037] <Crushing process: Step S2> 3 and 4(b), the heated metal material M is placed between the upper die 41 and the lower die 42 of the first forging die 40, and the upper die 41 is lowered relative to the lower die 42 by operating a press machine, thereby forming both end portions of the metal material M into a tapered shape suitable for centering. In this way, a first intermediate material 100 having both end portions formed into a tapered shape can be obtained.

[0038] <Rough forming process (hot forging process): Step S3> 3 and 4(c), the first intermediate material 100 is placed between the upper mold 51 and the lower mold 52 of the second forging die 50, and the upper mold 51 is lowered relative to the lower mold 52 by operating a press machine, thereby forming a pre-rotor core 210 having a pre-cylindrical portion 220, a pre-convex portion 221, and a pre-recessed portion 222, and forming a pre-shaft 211 having a pre-first shaft portion 211a and a pre-second shaft portion 211b. In this way, the second intermediate material 200 in which the pre-rotor core 210 and the pre-shaft 211 are formed can be obtained.

[0039] <Finishing forming process (hot forging process): Step S4> 3 and 4(d), the second intermediate material 200 is placed between the upper mold 61 and the lower mold 62 of the third forging die 60, and the upper mold 61 is lowered relative to the lower mold 62 by operating a press machine, thereby forming the pre-machined rotor core 10 having the pre-machined cylindrical portion 20, the pre-machined convex portion 21, and the essentially concave portion 22, as well as forming the pre-machined shaft 11 having the pre-machined first shaft portion 11a and the pre-machined second shaft portion 11b, and further forming the pre-machined flange-shaped portion 30. In this way, the third intermediate material 300 in which the pre-machined rotor core 10, the pre-machined shaft 11, and the pre-machined flange-shaped portion 30 are formed can be obtained.

[0040] <Machining process: Step S5> Then, as shown in step S5 of Fig. 3 and Fig. 5, in the third intermediate material 300 shown by the two-dot chain line in Fig. 5, the rotor core 10 excluding the recessed portion 22, the shaft 11, and the flange-like portion 30 are each subjected to machining (cutting, polishing, etc.) to obtain the forged integral rotor 3 as a product shown by the solid line in Fig. 5. Note that machining may be performed on either the shaft 11 or the flange-like portion 30.

[0041] The forged one-piece rotor 3 obtained in this manner has the rotor core 10 and shaft 11 integrally formed by forging, so not only does it not require the ring (nut) that was previously required, but it also reduces the number of parts and labor required compared to when a conventional assembled rotor is used as a rotor for a reluctance motor, and it also improves mechanical strength and rotational balance.

[0042] As shown in Figure 1(b), balance holes 31 are formed as needed in the axial end surface of the flange-shaped portion 30 of the forged integral rotor 3. This makes it possible to correct the mass imbalance with respect to the center of rotation of the forged integral rotor 3, thereby eliminating the mass imbalance and further improving the rotational balance. As a result, vibration during rotation is suppressed, enabling smooth rotation.

[0043] In the forged solid rotor 3, the protrusions 21 on the outer periphery of the rotor core 10 are machined, so that the air gap G between the protrusions 21 on the rotor core 10 and the inner periphery of the stator 2, as shown in the enlarged view of a main portion in FIG. 1( a), can be kept small and uniform around the entire circumference. By keeping the air gap G small, the magnetic field between the forged solid rotor 3 and the stator 2 is strengthened, improving the density of the transmittable power. Furthermore, by making the air gap G uniform around the entire circumference, changes in magnetic flux in the air gap G are suppressed, allowing current to flow balanced. Furthermore, in the forged solid rotor 3, the portions of the shaft 11 that are supported by bearings (the first bearing fitting portion 25 and the second bearing fitting portion 26) are machined, so that the dimensional tolerances can be kept within the range required for a shaft diameter that allows the bearings to be properly fitted.

[0044] While the forged rotor, the method for manufacturing the forged rotor, and the forging die of the present invention have been described above based on one embodiment, the present invention is not limited to the configuration described in the above embodiment, and the configuration can be appropriately modified within the scope of the spirit of the present invention. Specific alternative embodiments are as follows:

[0045] (Another embodiment) FIG. 6 is an explanatory diagram of a forged solid rotor 3′ according to another embodiment of the present invention. FIG. 6(a) is a plan view, and FIG. 6(b) is a side view. As shown in FIGS. 6(a) and 6(b), the present invention can also be applied to a rotor for an induction motor. In the forged solid rotor 3′ for an induction motor shown in FIGS. 6(a) and 6(b), components that are the same as or similar to those in the forged solid rotor 3 shown in FIGS. 1(a) and 1(b) are designated by the same reference numerals, and detailed descriptions thereof will be omitted. Note that the forged solid rotor 3′ shown in FIGS. 6(a) and 6(b) is manufactured using the same manufacturing method as the forged solid rotor 3 described above, and then aluminum is filled into the recesses 22 by a casting method. [Industrial Applicability]

[0046] The forged integral rotor of the present invention is suitable for use as a rotor to be incorporated into a stator in, for example, a reluctance motor, an induction motor, etc. It can also be used as a rotor for a generator. [Explanation of symbols]

[0047] 1 Reluctance motor 3,3´ Forged integral rotor 10 rotor core 11 Shaft 21 Convex part 22 recess 30 flange-shaped portion 31 Balance hole 60 Forging molds 61 Upper mold 62 Lower mold 63 Cavity 64 Rotor core forming section 65 Shaft forming section 66 Flange-shaped portion forming portion

Claims

1. A forged integral rotor for a motor, a rotor core having a protrusion and a recess on an outer periphery thereof; a shaft that is coaxially integrated with the rotor core; A forged integral rotor comprising:

2. 2. The forged integral rotor according to claim 1, wherein the shaft includes a flange-shaped portion in which a balance hole can be formed.

3. A method for manufacturing a forged integral rotor for a motor, comprising: A method for manufacturing a forged integral rotor includes a hot forging process in which a metal material is hot forged to form a rotor core having protrusions and recesses on its outer periphery, and a shaft that is integrated and coaxial with the rotor core.

4. 4. The method for manufacturing a forged integral rotor according to claim 3, further comprising a machining step of machining at least one of the rotor core and the shaft.

5. A forging die having an upper die and a lower die for manufacturing a forged integral rotor for a motor, The cavity formed by the upper mold and the lower mold is a rotor core forming section for forming a rotor core having a protrusion and a recess on an outer circumferential side; a shaft forming portion for forming a shaft that is coaxial with and integrated with the rotor core; A forging die having:

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