Rotor of a rotating electric machine

Abstract

The present invention provides a rotor for a rotating electric machine that allows for easy removal of permanent magnets embedded in the rotor core. [Solution] The rotor 1 of the rotating electric machine comprises a rotor core 10 in which a plurality of circular steel plates 10a, 10a are stacked and a plurality of slots 13 are formed that penetrate in the direction of stacking the steel plates 10a, a rotating shaft 12 disposed along the central axis CL of the rotor core 10, and plate-shaped permanent magnets 14 inserted into each slot 13. A gap D is formed between the surface 14f of the permanent magnet 14 and the wall surface 13f that forms the slot 13, and magnetic fluid 16 is filled into the gap D.

Description

Technical Field

[0001] The present invention relates to a rotor of a rotating electrical machine.

Background Art

[0002] Conventionally, as a rotor of a rotating electrical machine, a rotor in which permanent magnets are embedded has been proposed. For example, Patent Document 1 proposes a rotor including a rotor core in which a plurality of circular steel plates are laminated and slots penetrating in the axial direction are formed, and plate-shaped permanent magnets embedded in the respective slots. A gap is formed between the surface of the permanent magnet and the wall surface forming the slot, and the gap is filled with a resin material. Thereby, insulation between the permanent magnet and the rotor core can be ensured, and the permanent magnet can be fixed to the rotor core with the resin material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique disclosed in Patent Document 1, since the filled resin is filled in a cured state, the permanent magnet is firmly fixed to the rotor core. Therefore, when attempting to recycle the permanent magnet fixed to the rotor, the permanent magnet cannot be easily removed from the rotor core.

[0005] The present invention has been made in view of such points, and an object thereof is to provide a rotor of a rotating electrical machine in which a permanent magnet inserted into a slot of a rotor core can be easily removed.

Means for Solving the Problems

[0006] In view of the above problems, the rotor of a rotating electric machine according to the present invention comprises a rotor core formed by laminating a plurality of circular steel plates and having a plurality of slots formed through in the lamination direction of the steel plates, a rotating shaft disposed along the central axis of the rotor core, and plate-shaped permanent magnets inserted into each of the slots, wherein a gap is formed between the surface of the permanent magnet and the wall surface forming the slot, and the gap is filled with magnetic fluid.

[0007] According to the present invention, since magnetic fluid is filled in the gap between the surface of the permanent magnet and the wall surface forming the slot, the permanent magnet can be fixed to the rotor core by the magnetic force of the permanent magnet via the magnetic fluid. Furthermore, when removing the permanent magnet from the rotor core, the magnetic fluid acts as a lubricant, allowing the permanent magnet to slide against the rotor core along the lamination direction. As a result, the permanent magnet can be easily removed from the slot of the rotor core compared to the conventional method of fixing the permanent magnet to the rotor core via a resin material. The removed permanent magnet can be recycled simply by wiping off the magnetic fluid from its surface.

[0008] In a more preferred embodiment, the magnetic fluid is a magnetic fluid in which magnetic particles are dispersed in insulating oil. According to this embodiment, by using an oil that is generally highly electrically insulating, the conductivity between the rotor core and the permanent magnet can be suppressed by the insulating oil. This suppresses the formation of an eddy current circuit between the rotor core and the permanent magnet when the rotating electric machine is driven, thereby suppressing a decrease in the torque efficiency of the rotating electric machine. [Effects of the Invention]

[0009] According to the present invention, permanent magnets inserted into the slots of the rotor core can be easily removed. [Brief explanation of the drawing]

[0010] [Figure 1](a) is a schematic perspective view of the rotor of a rotating electric machine according to an embodiment of the present invention, and (b) is a schematic perspective view of a magnet embedded in the rotor core shown in (a). [Figure 2] Figure 1(a) is a plan view of the rotor core. [Figure 3] (a) is a cross-sectional view taken along line AA in Figure 2, and (b) is a cross-sectional view taken along line BB in Figure 2. [Figure 4] Figure 3(b) is a schematic, partially enlarged cross-sectional view. [Modes for carrying out the invention]

[0011] The rotor 1 of a rotating electric machine according to an embodiment of the present invention will be described below with reference to Figures 1 to 4. Figure 1(a) is a schematic perspective view of the rotor 1 of a rotating electric machine according to an embodiment of the present invention, and Figure 1(b) is a schematic perspective view of the permanent magnet 14 embedded in the rotor core 10 shown in Figure 1(a).

[0012] As shown in Figure 1(a), the rotor 1 of the rotating electric machine according to this embodiment is a rotor used in an IPM (Interior Permanent Magnet) motor. The rotor 1 comprises a rotor core 10, a rotating shaft 12 fixed to the rotor core 10, and a plurality of permanent magnets 14, 14, ... embedded in the rotor core 10.

[0013] The rotor core 10 is cylindrical and is a laminate formed by stacking multiple circular steel plates 10a, 10a, ... such as electromagnetic steel plates. In this embodiment, the steel plates 10a are connected and fixed to each other by crimping or the like, but the electromagnetic steel plates may be connected to each other via an insulating resin.

[0014] Examples of the soft magnetic material constituting the rotor core 10 (steel plate 10a) include, but are not limited to, those composed of at least one magnetic metal selected from the group consisting of Fe, Co, and Ni, and at least one non-magnetic metal selected from the group consisting of B, C, P, Al, Si, Ti, V, Cr, Mn, Cu, Y, Zr, Nb, Mo, Hf, Ta, and W.

[0015] The rotating shaft 12 is disposed along the central axis CL of the rotor core 10. Specifically, the axis of the columnar rotor core 10 is the central axis about which the rotor 1 rotates, and a through-hole 11 having a circular shape in plan view is formed on the central axis of the rotor core 10. The rotating shaft 12 of the rotating electric machine is fixed in a state of being inserted through the through-hole 11.

[0016] Each permanent magnet 14 is embedded in the rotor core 10. Specifically, a plurality of slots 13, 13,... penetrating in the stacking direction of the steel plate 10a (the direction along the central axis CL) are formed in the outer peripheral portion of the rotor core 10. Each permanent magnet 14 is fixed in a state of being inserted into each slot 13.

[0017] As the permanent magnet 14, a magnet containing a rare earth metal is used. Examples of the rare earth magnet include rare earth magnets such as a neodymium magnet mainly composed of neodymium, iron, and boron, and a samarium cobalt magnet mainly composed of samarium and cobalt. The permanent magnet 14 may be a ferrite magnet, an alnico magnet, or the like other than these.

[0018] As shown in Fig. 1(b), the permanent magnet 14 is formed in a plate shape, and the permanent magnet 14 has six surfaces including a pair of end faces 14a, 14a, narrow-width faces 14b, 14b, and a pair of wide-width faces 14c, 14c. In the present embodiment, on one side of the wide-width face 14c side, the permanent magnet 14 is magnetized to the N pole, and on the other side of the wide-width face 14c, it is magnetized to the S pole. The pair of wide-width faces 14c, 14c are the surfaces that form the magnetic poles. The wide-width faces 14c, 14c of the permanent magnet 14 are the surfaces through which the magnetic flux J1(J) passes, and a magnetic flux J2(J) that circulates between one wide-width face 14c and the other wide-width face 14c is formed.

[0019] Note that the surfaces of the permanent magnet 14 referred to in the present invention are the pair of narrow-width faces 14b, 14b and the pair of wide-width faces 14c, 14c. In the following specification, when collectively referring to these, they are referred to as the surface 14f of the permanent magnet 14. Further, in the following specification, among the wall surfaces that form the slot 13 to be described later, the wall surface facing each narrow-width face 14b is referred to as the wall surface 13b, and among the wall surfaces that form the slot 13 to be described later, the wall surface facing each wide-width face 14c is referred to as the wall surface 13c. Further, these wall surfaces 13b, 13c are referred to as the wall surface 13f of the slot 13.

[0020] Fig. 2 is a plan view of the rotor core shown in Fig. 1(a). As shown in Fig. 2, in the present embodiment, each slot 13 is rectangular in plan view, and two adjacent slots 13, 13 are formed side by side in plan view, and these are formed every 90° around the rotation axis (central axis CL). A permanent magnet 14 is inserted into each of the two adjacent slots 13 to constitute one magnetic field. Therefore, in the rotor core 10, a total of eight slots 13, 13... are inserted with eight permanent magnets 14, 14..., and a total of four magnetic poles are formed on the outer peripheral portion of the rotor core 10.

[0021] Figure 3(a) is a cross-sectional view taken along line AA in Figure 2, and Figure 3(b) is a cross-sectional view taken along line BB in Figure 2. As shown in Figures 3(a) and (b), the permanent magnet 14 is formed with dimensions of thickness T1, width W1, and length L1, and the slot 13 is formed with dimensions of vertical width (thickness) T2, horizontal width W2, and length L2. The thickness T1 of the permanent magnet 14 is smaller than the vertical width T2 of the slot 13. Furthermore, the width W1 of the permanent magnet 14 is smaller than the horizontal width W2 of the slot 13. Furthermore, the length L1 of the permanent magnet 14 is the same as the length L2 of the slot 13.

[0022] As a result, a gap D is formed between the surface 14f of the permanent magnet 14 and the wall surface 13f that forms the slot 13. Specifically, as shown in Figure 3(a), the narrow surface 14b of the permanent magnet 14 and the wall surface 13b of the slot 13 are opposing planes, and a gap D1 is formed between the narrow surface 14b of the permanent magnet 14 and the wall surface 13b of the slot 13. Furthermore, as shown in Figures 3(b) and 4, the wide surface 14c of the permanent magnet 14 and the wall surface 13c of the slot 13 are opposing planes, and a gap D2 is formed between the wide surface 14c of the permanent magnet 14 and the wall surface 13c of the slot 13.

[0023] In this embodiment, magnetic fluid 16 is filled in the gap D between the surface 14f of the permanent magnet 14 and the wall surface 13f that forms the slot 13. In this embodiment, magnetic fluid 16 is filled in both the gap D1 between the narrow surface 14b of the permanent magnet 14 and the wall surface 13b of the slot 13, and the gap D2 between the wide surface 14c of the permanent magnet 14 and the wall surface 13c of the slot 13.

[0024] When filling with magnetic fluid 16, the magnetic fluid 16 is applied to both sides of the pair of wide surfaces 14c, 14c and the pair of narrow surfaces 14b, 14b of the permanent magnet. Furthermore, the magnetic fluid 16 is poured into the slot 13 of the rotor core 10, causing the magnetic fluid 16 to adhere to the wall surface 13f (13b, 13c). In this state, the permanent magnet 14 is inserted through one opening of the slot 13. This allows each permanent magnet 14 to be embedded in the rotor core 10 with the magnetic fluid 16 filling the gap D between the surface 14f of the permanent magnet 14 and the wall surface 13f forming the slot 13. Alternatively, the magnetic fluid 16 may be filled into the gap D by inserting the permanent magnet 14 into the slot 13 while the rotor core 10 is immersed in a tank containing magnetic fluid 16.

[0025] The magnetic fluid 16 is a functional fluid that, despite being a fluid, is magnetic and is attracted to the permanent magnet 14 like iron filings. In this embodiment, the magnetic fluid 16 is a fluid in which magnetic particles (magnetic fine particles) are dispersed in a dispersion medium. A surfactant may be attached to the surface of the magnetic particles to enhance their dispersibility in the dispersion medium.

[0026] Examples of materials for the magnetic particles constituting the magnetic fluid 16 include iron, nickel, cobalt, carbonyl iron, iron alloys, iron oxide, iron nitride, iron carbide, low-carbon steel, rare earth elements, mixtures thereof, or alloys of two or more of these. For example, ferromagnetic particles (ferromagnetic fine particles) such as magnetite and manganese zinc ferrite may be used, or soft magnetic particles (soft magnetic fine particles) such as low-carbon steel may be used.

[0027] In particular, ferromagnetic particles such as magnetite are less likely to affect the magnetic field generated from the permanent magnet 14 because magnetite is a ferromagnetic material. Furthermore, because magnetite is an iron oxide, it is easy to ensure electrical insulation between the permanent magnet 14 and the rotor core 10. In addition, since the ferromagnetic particles are also attracted to the wall surface 13f of the slot 13, it is easier to fill the gap D between the surface 14f of the permanent magnet 14 and the wall surface 13f forming the slot 13 with magnetic fluid 16 and to retain the magnetic fluid 16.

[0028] Examples of dispersion media constituting the magnetic fluid 16 include ester oils such as polyol esters, diesters, and complex esters; hydrocarbon oils such as isoparaffins, polyalphaolefins, alkylnaphthalenes, and polyethers; or silicone oils (fluorine oils) such as dimethyl silicone, modified silicone, and diethyl silicone.

[0029] Among these, the dispersion medium is preferably insulating oil. This makes it possible to suppress the formation of an eddy current circuit between the permanent magnet 14 and the rotor core 10 when the rotating electric machine is driven, thereby suppressing a decrease in the output efficiency of the rotating electric machine.

[0030] The electrical resistivity ρ of the dispersion medium is 10 10 ~10 18 It is preferable that it be in the range of Ω·m. The larger the electrical resistivity ρ, the better, and the upper limit of electrical resistivity ρ is 10 18 Ω·m is a value for insulating oil that can also satisfy the following characteristics of the dispersion medium: the lower limit of the electrical resistivity ρ of the dispersion medium, 10 10 If the value falls below Ω·m, the permanent magnet 14 and the electromagnetic steel sheet will conduct electricity, which may cause an increase in rotational electric machine losses (a decrease in the output efficiency of the rotational electric machine) due to the generation of an eddy current circuit through the magnet and the electromagnetic steel sheet.

[0031] Furthermore, the relative permeability μr of the dispersion medium is preferably in the range of 1 to 2. This reduces the impairment of the magnetic flux flow of the permanent magnet 14 passing through the magnetic fluid. Here, the larger the relative permeability μr, the better, and the upper limit of relative permeability μr, 2, is the value for a dispersion medium that can be manufactured by general methods. If the relative permeability μr of the dispersion medium falls below the lower limit of 1, it may cause a decrease in the output of the rotating electric machine, similar to the case where air or resin is interposed in the gap D between the surface 14f of the permanent magnet 14 and the wall surface 13f forming the slot 13.

[0032] Furthermore, the boiling point of the dispersion medium is preferably in the range of 160 to 400°C. This prevents the dispersion medium from evaporating even if the rotor 1 is heated when the rotating electric machine is driven. Here, the higher the boiling point of the dispersion medium, the better, and 400°C, the upper limit of the boiling point of the dispersion medium, is the value for dispersion medium that can be manufactured by general methods. If it falls below the lower limit of the boiling point of the dispersion medium, 160°C, the rotor 1 may be heated when the rotating electric machine is driven, and the dispersion medium may evaporate (vaporize). This may prevent the permanent magnets 14 from being held in the rotor core 10 via the magnetic fluid 16.

[0033] As a dispersion medium having these properties, isoparaffin (electrical resistivity ρ: 10 12 Ω·m, relative permeability μr: 1, boiling point: 160℃), alkylnaphthalene (electrical resistivity ρ: 10 10 Ω·m, relative permeability μr: 1, boiling point: 400℃), polyalphaolefin (electrical resistivity ρ: 10 12 Ω·m, relative permeability μr: 1, boiling point: 300℃), or fluorine oil (electrical resistivity ρ: 10 18 (Ω·m, relative permeability μr: 2, boiling point: 200℃) can be cited.

[0034] According to this embodiment, as shown in Figure 4, the gap D between the surface 14f of the permanent magnet 14 and the wall surface 13f forming the slot 13 is filled with magnetic fluid 16. Therefore, the permanent magnet 14 can be fixed to the rotor core 10 by the magnetic force (magnetic flux J) of the permanent magnet 14 via the magnetic fluid 16.

[0035] By using insulating oil as the dispersion medium for the magnetic fluid 16, conductivity between the permanent magnet 14 and the rotor core 10 can be suppressed when the rotating electric machine is in operation, so that an eddy current circuit C1 is formed only in the permanent magnet 14. Therefore, it is possible to prevent the formation of an eddy current circuit C2 between the permanent magnet 14 and the rotor core 10. As a result, the decrease in the output efficiency of the rotating electric machine can be suppressed.

[0036] Furthermore, when removing the permanent magnet 14 from the rotor core 10, the magnetic fluid 16 acts as a lubricant, allowing the permanent magnet 14 to slide relative to the rotor core 10 along the lamination direction. This makes it easier to remove the permanent magnet 14 from the slot 13 of the rotor core 10 compared to the conventional method of fixing the permanent magnet to the rotor core via a resin material. The permanent magnet 14 can be recycled simply by wiping off the magnetic fluid from the surface 14f of the removed permanent magnet 14, thereby improving the recyclability of the permanent magnet 14.

[0037] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various design modifications can be made without departing from the spirit of the invention as described in the claims. [Explanation of Symbols]

[0038] 1: Rotor of a rotating electric machine, 10: Rotor core, 10a: Steel plate, 11: Through hole, 12: Rotating shaft, 13: Slot, 13f: Wall surface, 14: Permanent magnet, 14b: Narrow surface, 14c: Wide surface (surface), 16: Magnetic fluid, CL: Central axis

Claims

1. A rotor for a rotating electric machine comprising: a rotor core formed by laminating multiple circular steel plates and having multiple slots extending through the lamination direction of the steel plates; a rotating shaft disposed along the central axis of the rotor core; and plate-shaped permanent magnets inserted into each of the slots, A gap is formed between the surface of the permanent magnet and the wall surface forming the slot. The rotor of a rotating electric machine is characterized in that the gap is filled with magnetic fluid.

2. The rotor of the rotating electric machine according to claim 1, characterized in that the magnetic fluid is a magnetic fluid obtained by dispersing magnetic particles in insulating oil.

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