Rotor and manufacturing method for same

Abstract

Provided is a rotor that can suppress the extension of a bridge between magnet holes due to plastic deformation during high-speed rotation. This invention includes: an iron columnar rotor core 3; a plurality of magnet holes 5 provided, in the circumferential direction, to the rotor core 3; a plurality of magnets 7 respectively fixed to the plurality of magnet holes 5; and a bridge 9 between magnet holes 5 adjacent in the circumferential direction. The bridge 9 is a plastic deformation part in a tensile plastic deformation state in the radial direction of the rotor core 3.

Description

Rotor and manufacturing method thereof

[0001] The present invention relates to a rotor for use in a rotating electrical machine such as an electric motor, and a method for manufacturing the same.

[0002] An example of a conventional rotor is the rotor disclosed in Patent Document 1. This rotor includes a sleeve that covers the outer circumferential surface of a rotor core having magnet holes in which permanent magnets are disposed and bridges between the magnet holes.

[0003] It is said that with such a rotor, even if the bridge is made thinner to reduce leakage flux, high speed rotation is possible because the strength is maintained by the sleeve.

[0004] However, when the rotor rotates at high speed, the bridges sometimes undergo plastic deformation exceeding the yield stress and elongate in the radial direction. If a large gap is provided between the rotor and the stator to allow for this elongation, the output of the rotating electrical machine will decrease.

[0005] Patent No. 7130051

[0006] The problem to be solved is that the bridge between the magnet holes may be stretched due to plastic deformation during high speed rotation.

[0007] The present invention provides a rotor including a cylindrical rotor core, a plurality of magnet holes provided in the rotor core in the circumferential direction, a plurality of magnets respectively fixed to the plurality of magnet holes, and a bridge between adjacent magnet holes in the circumferential direction, wherein the bridge is a plastically deformed portion in a tensile plastic deformation state in the radial direction of the rotor core.

[0008] The present invention also provides a method for manufacturing a rotor, which includes forming a semi-finished product in which a cylindrical rotor core has a plurality of magnet holes in the circumferential direction, and which defines bridges between adjacent magnet holes in the circumferential direction, and plastically deforming the bridges of the semi-finished product by pulling the rotor core in the radial direction to form plastically deformed portions in a tensile plastic deformation state.

[0009] The present invention can prevent the bridges between the magnet holes from being elongated due to plastic deformation during high-speed rotation.

[0010] Fig. 1 is a plan view of a rotor according to an embodiment of the present invention. Fig. 2 is an enlarged plan view showing a portion of the rotor of Fig. 1. Fig. 3 is an enlarged plan view showing forces acting when the bridges of the rotor of Fig. 1 are tensioned. Fig. 4 is a stress-strain curve of a semi-finished rotor core according to the embodiment. Fig. 5 is a plan view showing a portion of a rotor according to a modified example.

[0011] The rotor 1 includes a rotor core 3, a plurality of magnet holes 5, a plurality of magnets 7, and bridges 9. The rotor core 3 is a columnar member. The plurality of magnet holes 5 are provided in the rotor core 3 in the circumferential direction. The plurality of magnets 7 are fixed to the plurality of magnet holes 5, respectively. The bridges 9 are portions located between adjacent magnet holes 5 in the circumferential direction. The bridges 9 are plastically deformed portions that are in a tensile plastic deformation state in the radial direction of the rotor core 3.

[0012] The rotor 1 may include a sleeve 13 that is stronger than the rotor core 3 and that is fitted onto the outer peripheral surface 3 a of the rotor core 3 .

[0013] In this case, the magnet holes 5 preferably open to the outer peripheral surface 3 a of the rotor core 3 .

[0014] The manufacturing method of the rotor 1 involves forming a semi-finished product 14 in which a cylindrical rotor core 3 is provided with a plurality of magnet holes 5 in the circumferential direction, and bridges 9 are defined between adjacent magnet holes 5 in the circumferential direction. The bridges 9 of the semi-finished product 14 are then plastically deformed by tension in the radial direction of the rotor core 3, to form plastically deformed portions in a tensile plastically deformed state.

[0015] The bridge 9 is preferably plastically deformed by applying a stress greater than that acting on the bridge 9 when used as a rotating electrical machine. For example, the bridge 9 is pulled so as to apply a stress greater than that acting on the bridge 9 at the maximum rotation speed.

[0016] Any suitable method can be used to plastically deform the bridge 9. In one embodiment, a plurality of magnets 7 are placed in each of the plurality of magnet holes 5 in the semi-finished product 14, and resin G for fixing each magnet 7 is filled into each magnet hole 5, and the bridge 9 is plastically deformed by the filling pressure of the resin G. In another embodiment, the bridge 9 can be mechanically pulled before filling with the resin G. This pulling of the bridge 9 can be performed by hooking a fingernail into the magnet holes 5 on both sides of the bridge 9, for example.

[0017] The magnet hole 5 may open to the outer peripheral surface 3a of the rotor core 3, and a sleeve 13 having greater strength than the rotor core 3 may be fitted onto the outer peripheral surface 3a of the rotor core 3 before the resin is filled.

[0018] [Rotor] Fig. 1 is a plan view of a rotor according to an embodiment of the present invention. Fig. 2 is an enlarged plan view showing a part of the rotor according to the embodiment. In the following description, the axial direction refers to the direction along the axis of the rotor (the direction perpendicular to the plane of the paper in Fig. 1), and the radial direction and circumferential direction refer to the radial direction and circumferential direction, respectively, centered on the axis of the rotor.

[0019] As shown in FIG. 1 , the rotor 1 includes a rotor core 3 , a plurality of magnet holes 5 , a plurality of magnets 7 , and bridges 9 .

[0020] The rotor core 3 is a columnar, particularly cylindrical, member and is formed by stacking and integrating a plurality of plate materials, for example, punched from magnetic steel plate or silicon steel plate, in the axial direction. However, the rotor core 3 may also be formed from a single columnar member. The rotor core 3 has a hole 11 that penetrates in the axial direction at its center.

[0021] The plurality of magnet holes 5 are provided at intervals in the circumferential direction near the outer periphery of the rotor core 3. These magnet holes 5 are holes that pass through the rotor core 3 in the axial direction.

[0022] Each of the multiple magnet holes 5 is formed in a substantially rectangular shape in a plan view. These magnet holes 5 are arranged at an angle such that the distance between pairs of magnet holes 5 in the circumferential direction increases from the inside to the outside in the radial direction. In this embodiment, multiple pairs of magnet holes 5, for example, eight pairs, are arranged in the circumferential direction with a constant distance between the pairs.

[0023] The radial outside of the magnet holes 5 reaches the outer peripheral surface 3a of the rotor core 3. As a result, the magnet holes 5 open at the outer peripheral surface 3a of the rotor core 3. However, the magnet holes 5 may have a closed cross-sectional shape in plan view without opening at the outer peripheral surface 3a of the rotor core 3.

[0024] As shown in FIG. 2, each magnet hole 5 is defined by one edge 5a, another edge 5b, and an end edge 5c in plan view.

[0025] One edge 5a extends linearly along the slope of the magnet hole 5. The other edge 5b is formed parallel to this one edge 5a. The other edge 5b has a step 5ba formed between the first and second other edge portions 5bb and 5bc. The end edge 5c is located between the one edge 5a and the other edge portion 5b on the radially inner side of the pair of magnet holes 5. The end edge 5c is arranged parallel to the radial direction.

[0026] A first curved portion 5d is formed between the first edge 5a and the end edge 5c, and a second curved portion 5e is formed between the second edge 5b and the end edge 5c. The first curved portion 5d on the radially inner side has a smaller radius of curvature than the second curved portion 5e on the outer side.

[0027] The multiple magnets 7 are rod-shaped permanent magnets, each fixed in one of the multiple magnet holes 5. Each magnet 7 is rectangular in plan view and is positioned between one edge 5a and a first other edge 5bb of the magnet hole 5. The radially outer end of each magnet 7 is engaged with a step 5ba to position it. In this state, each magnet 7 is fixed in place by the resin G that has hardened within the magnet hole 5.

[0028] Resin G is filled and hardened within each magnet hole 5, between the magnet 7 and the edge portion 5c of the magnet hole 5, between the magnet 7 and the first other edge portion 5bb of the magnet hole 5, and between the magnet 7 and the inner surface of the sleeve 13.

[0029] The bridges 9 are portions located between the edge portions 5c of adjacent pairs of magnet holes 5. The bridges 9 are plastically deformed portions that are in a tensile plastic deformation state in the radial direction of the rotor core 3. The tensile plastic deformation state refers to a state in which the bridges 9 extend radially due to plastic deformation relative to the state in which the plate material that constitutes the rotor core 3 is punched out.

[0030] In this embodiment, the outer diameter of the rotor core 3 remains almost unchanged regardless of whether the bridges 9 are in a tensile plastic deformation state. However, the rotor core 3 may partially protrude in the radial direction due to the tensile plastic deformation of the bridges 9.

[0031] The bridges 9 are preferably plastically deformed by applying a stress greater than that acting on the bridges 9 when used as a rotating electrical machine. For example, the bridges 9 are pulled so as to apply a stress greater than that acting on the bridges 9 at the maximum rotation speed, thereby causing the bridges 9 to plastically deform. This pulling of the bridges 9 is performed by utilizing the filling pressure of the resin G, as will be described later.

[0032] However, it is also possible to mechanically pull the bridge 9 without using the filling pressure of the resin G. This pulling of the bridge 9 can be performed by hooking a nail into the magnet hole 5 on both sides of the bridge 9, for example.

[0033] The sleeve 13 is a cylindrical member that fits onto the outer peripheral surface 3a of the rotor core 3. The sleeve 13 is made of CFRP, titanium alloy, Inconel, or the like, and is set to have a strength that is relatively high compared to that of the rotor core 3. The sleeve 13 can be fitted onto the outer peripheral surface 3a of each rotor core 3 by an interference fit, an interference fit, a clearance fit, or the like.

[0034] [Method of Manufacturing a Rotor] FIG. 3 is an enlarged plan view of a part of the semi-finished product 14 of the rotor 1, showing the forces acting when the bridge 9 is pulled.

[0035] The manufacturing method of the rotor 1 begins by sequentially stacking and integrating a plurality of plate materials in the axial direction to form the rotor core 3. The plate materials may be integrated by appropriately using welding, caulking, adhesive, or the like.

[0036] The rotor core 3 of this embodiment has magnet holes 5, bridges 9, holes 11, etc. formed in plate material. Therefore, the formed columnar rotor core 3 has multiple magnet holes 5 in the circumferential direction, and constitutes a semi-finished product 14 in which bridges 9 are defined between adjacent magnet holes 5 in the circumferential direction. Note that if the rotor core 3 is to be a single columnar shape, the magnet holes 5 may be formed later and the bridges 9 may be defined to form the semi-finished product 14.

[0037] The semi-finished product 14 of this embodiment has the sleeve 13 attached to the outer peripheral surface 3a of the rotor core 3. The sleeve 13 may be attached by an interference fit, a snug fit, a loose fit, or the like, as described above.

[0038] The bridges 9 of the semi-finished product 14 are plastically deformed by tension in the radial direction of the rotor core 3, to form plastically deformed portions in a tensile plastic deformation state. The plastic deformation of the bridges 9 is performed by utilizing the filling pressure of the resin G as described above.

[0039] That is, after inserting magnets 7 into each magnet hole 5, resin G is filled in. By adjusting the filling pressure of the resin G at this time, radial tensile stress is applied to the bridges 9, causing plastic deformation of the bridges 9 so that they are elongated in the radial direction.

[0040] FIG. 4 is a stress-strain diagram of the semi-finished rotor core 3.

[0041] As shown in Figure 3, when resin G is filled into the magnet holes 5, stress f due to the pressure of the resin G acts on each surface of the end edge portion 5c (see Figure 2), one edge portion 5a (see Figure 2), first other edge portion 5bb (see Figure 2), and first and second curved portions 5d and 5e (see Figure 2) of each magnet hole 5.

[0042] At this time, the radially outer opening of the magnet hole 5 is closed by the strong sleeve 13, which prevents the pressure of the resin G from escaping to the sleeve 13 side. Therefore, the stress f due to the pressure of the resin G can be reliably applied to the edge of the magnet hole 5.

[0043] This stress f causes a compressive stress in the width direction and a tensile stress F in the radial direction to act on each bridge 9. In this embodiment, the tensile stress F of each bridge 9 exceeds the yield stress of the bridge 9 and also exceeds the tensile stress acting on the bridge 9 at the maximum rotation speed of the electric motor. This tensile stress F causes tensile plastic deformation of each bridge 9 in the radial direction.

[0044] That is, the bridge 9 of this embodiment is tensile plastically deformed in advance by the tensile stress F that exceeds the tensile stress B that acts on the bridge 9 at the maximum rotation speed of the electric motor, as shown in Figure 4. Therefore, even if the bridge 9 is subjected to the tensile stress B at the maximum rotation speed of the electric motor, the bridge 9 does not elongate or the elongation is kept within an allowable range.

[0045] It should be noted that the tensile stress F can be made lower than the tensile stress B as long as the elongation of the bridge 9 can be suppressed within an allowable range.

[0046] On the other hand, if the bridge 9 does not undergo tensile plastic deformation, when the bridge 9 receives tensile stress B at the maximum rotation speed of the electric motor, the bridge 9 will stretch beyond the elastic deformation range A. This will cause the characteristics of the rotor 1 to fluctuate midway.

[0047] As described above, in this embodiment, the bridges 9 are configured as plastically deformed portions that are in a tensile plastic deformation state in the radial direction. Therefore, when the rotor 1 is used as an electric motor, which is a rotating electrical machine, the extension of the bridges 9 of the rotor 1 is suppressed to an allowable range or is eliminated.

[0048] This eliminates the need for a large gap between the rotor 1 and the stator of the electric motor, preventing performance degradation. It also prevents the characteristics of the rotor 1 and the electric motor using it, such as rotational balance, from fluctuating midway.

[0049] Furthermore, in this embodiment, the fatigue strength of the rotor 1 is improved due to the plastic strain of the bridges 9, and leakage flux from the rotor 1 can be suppressed, thereby improving the performance of the electric motor.

[0050] Furthermore, in this embodiment, the fatigue strength of the rotor 1 at the bridge 9 is improved, so that an increase in the thickness of the sleeve 13 can be suppressed or reduced, thereby improving the performance of the electric motor.

[0051] Furthermore, since the sleeve 13 and the rotor core 3 can be manufactured separately and then assembled together, the degree of freedom in the manufacturing process can be improved.

[0052] [Modification] FIG. 5 is a plan view showing a part of a rotor according to a modification.

[0053] The bridges 9 and 19 of the modified example are arranged at a location where the leakage magnetic flux is relatively large and at a location where the leakage magnetic flux is relatively small.

[0054] The bridges 9 in areas where the leakage magnetic flux is relatively large are plastically deformed portions that are in a tensile plastic deformation state in the radial direction of the rotor core 3. The bridges 19 in areas where the leakage magnetic flux is relatively small are in a non-plastically deformed state. In this way, the bridges 9 and the like can be appropriately made plastically deformed portions taking into account the amount of leakage magnetic flux.

[0055] In this modification, as shown in Fig. 5, a pair of magnet holes 15 is similarly arranged radially outward of each pair of magnet holes 5. These magnet holes 5 and 15 are arranged in the circumferential direction in, for example, eight pairs, as in Fig. 1.

[0056] The radially outer ends of the magnet holes 15 do not open to the outer peripheral surface 3 a of the rotor core 3, but are closed by bridges 21. Note that the radially outer ends of the magnet holes 15 may also open to the outer peripheral surface of the rotor core 3.

[0057] A magnet 7 is fixed to each magnet hole 5, and a magnet 17 is fixed to each magnet hole 15. The magnets 7 and 17 are fixed with resin G.

[0058] In this way, in this embodiment, when there are three or more magnets 7 and 17 in the region where the paired magnet holes 5 are located, the bridge 9 with the highest stress is the plastically deformed portion in a plastically deformed state. The bridge 19 becomes a path for the main magnetic flux by being in a non-plastically deformed state.

[0059] In this modified example, the same effects as those of the embodiment can be achieved.

[0060] REFERENCE SIGNS LIST 1 rotor 3 rotor core 3a outer peripheral surface 5 magnet hole 7 magnet 9 bridge 13 sleeve

Claims

1. A rotor comprising: a cylindrical rotor core; a plurality of magnet holes provided in the rotor core in the circumferential direction; a plurality of magnets fixed to each of the plurality of magnet holes; and a bridge between adjacent magnet holes in the circumferential direction, wherein the bridge is a plastically deformed portion that is in a tensile plastically deformed state in the radial direction of the rotor core.

2. The rotor according to claim 1, further comprising a sleeve that is fitted onto the outer peripheral surface of the rotor core and has greater strength than the rotor core.

3. A rotor according to claim 2, wherein the magnet holes are open to the outer peripheral surface of the rotor core.

4. A method for manufacturing a rotor, comprising forming a semi-finished product in which a cylindrical rotor core has a plurality of magnet holes in the circumferential direction and a bridge is defined between adjacent magnet holes in the circumferential direction, and plastically deforming the bridge of the semi-finished product by pulling the rotor core in the radial direction to form a plastically deformed portion in a tensile plastic deformation state.

5. A method for manufacturing a rotor according to claim 4, comprising the steps of: arranging a plurality of magnets in each of the plurality of magnet holes in the semi-finished product; filling each magnet hole with resin to fix each magnet; and plastically deforming the bridge by the filling pressure of the resin.

6. A method for manufacturing a rotor according to claim 5, wherein the magnet holes open to the outer peripheral surface of the rotor core, and a sleeve having greater strength than the rotor core is fitted onto the outer peripheral surface of the rotor core before the resin is filled.

7. A method for manufacturing a rotor according to claim 5 or 6, wherein the bridge is plastically deformed by pulling the bridge so as to apply a stress greater than that acting on the bridge at the maximum rotation speed of the rotating electric machine.

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