Rotor of an electric rotating machine

Abstract

A rotor of a rotary electric machine capable of easily taking out a permanent magnet buried in a rotor core. The rotor of the rotary electric machine includes a rotor core formed by stacking a plurality of circular steel sheets and formed with a plurality of slots penetrating in a stacking direction of the steel sheets, a rotary shaft disposed along a central axis of the rotor core, and a plate-shaped permanent magnet inserted into each slot. A gap is formed between a surface of the permanent magnet and a wall surface forming the slot, and a magnetic fluid is filled in the gap.

Description

Technical Field

[0001] This invention relates to a rotor of a rotary electric motor. Background Technology

[0002] Conventionally, rotors for rotating electrical machines have incorporated permanent magnets. For example, Patent Document 1 discloses a rotor comprising: a rotor core formed by stacking multiple circular steel plates and having axially penetrating slots; and plate-shaped permanent magnets embedded in each slot. A gap is formed between the surface of the permanent magnet and the wall of the slot, and this gap is filled with a resin material. This ensures insulation between the permanent magnet and the rotor core, and allows the permanent magnet to be fixed to the rotor core using the resin material.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2013-158149 Summary of the Invention

[0004] However, in the technology shown in Patent Document 1, since the filling resin is filled in a cured state, the permanent magnet is firmly fixed to the rotor core. Therefore, if it is desired to recycle the permanent magnet fixed to the rotor, it is not easy to remove the permanent magnet from the rotor core.

[0005] The present invention was made in view of this, and its object is to provide a rotor of a rotating electric motor in which a permanent magnet inserted into a slot in a rotor core can be easily removed.

[0006] In view of the above-mentioned issues, the rotor of the rotary electric machine according to the present invention comprises: a rotor core, which is formed by stacking multiple circular steel plates and having multiple slots extending through the stacking direction of the steel plates; a rotating shaft disposed along the central axis of the rotor core; and a plate-shaped permanent magnet inserted into each of the slots, wherein a gap is formed between the surface of the permanent magnet and the wall of the slot, and the gap is filled with a magnetic fluid.

[0007] According to the present invention, a magnetic fluid is filled in the gap between the surface of the permanent magnet and the wall of the groove, thus allowing the permanent magnet to 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 relative to the rotor core in the stacking direction. Therefore, compared to the conventional method of fixing the permanent magnet to the rotor core using resin material, the permanent magnet can be easily removed from the groove of the rotor core. The permanent magnet can be recycled simply by wiping the surface of the removed permanent magnet with the magnetic fluid.

[0008] As a more preferred embodiment, the magnetic fluid is a magnetic fluid in which magnetic particles are dispersed in insulating oil. According to this method, by also using an oil with generally high electrical insulation properties, the conduction between the rotor core and the permanent magnet can be suppressed. Therefore, when driving a rotating electric motor, the formation of eddy current circuits between the rotor core and the permanent magnet can be suppressed, thereby suppressing the reduction in the torque efficiency of the rotating electric motor.

[0009] Invention Effects

[0010] According to the present invention, the permanent magnet inserted into the slot of the rotor core can be easily removed. Attached Figure Description

[0011] Figure 1 (a) is a schematic perspective view of the rotor of a rotary electric machine according to an embodiment of the present invention. Figure 1 (b) is buried in Figure 1 (a) is a schematic perspective view of the magnet in the rotor core.

[0012] Figure 2 yes Figure 1 (a) is a top view of the rotor core.

[0013] Figure 3 (a) is along Figure 2 A sectional view cut along line AA. Figure 3 (b) is along Figure 2 A sectional view cut along the BB line.

[0014] Figure 4 It is a schematic representation Figure 3 (b) is a partially enlarged sectional view. Detailed Implementation

[0015] The following is for reference. Figures 1-4 The rotor 1 of the rotary electric machine according to the embodiments of the present invention will be described. Figure 1 (a) is a schematic perspective view of the rotor 1 of the rotary electric machine according to an embodiment of the present invention. Figure 1 (b) is buried in Figure 1 (a) is a schematic perspective view of the permanent magnet 14 in the rotor core 10 shown.

[0016] like Figure 1 As shown in (a), the rotor 1 of the rotary electric motor according to this embodiment is a rotor used in an interior permanent magnet (IPM) motor. The rotor 1 includes: 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.

[0017] The rotor core 10 is cylindrical and is a laminated body composed of multiple circular electromagnetic steel plates 10a, 10a, ... . In this embodiment, the steel plates 10a are connected and fixed to each other by riveting or the like, but the electromagnetic steel plates can also be connected to each other by an insulating resin.

[0018] As a soft magnetic material constituting the rotor core 10 (steel plate 10a), examples include materials 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, but not limited to these.

[0019] The rotating shaft 12 is disposed along the central axis CL of the rotor core 10. Specifically, the axis of the cylindrical rotor core 10 is the central axis of rotation of the rotor 1, and a through hole 11, which is circular when viewed from above, is formed on the central axis of the rotor core 10. The rotating shaft 12 of the rotary motor is fixed in the through hole 11.

[0020] Each permanent magnet 14 is embedded in the rotor core 10. Specifically, a plurality of slots 13, 13, ... are formed on the outer periphery of the rotor core 10, extending along the stacking direction of the steel plates 10a (along the direction of the central axis CL). A permanent magnet 14 is fixed in an inserted state in each slot 13.

[0021] The permanent magnet 14 is a magnet containing rare earth metals. Examples of rare earth magnets include neodymium magnets, which are mainly composed of neodymium, iron, and boron, and samarium cobalt magnets, which are mainly composed of samarium and cobalt. In addition to these, the permanent magnet 14 can also be a ferrite magnet, an AlNiCo magnet, etc.

[0022] like Figure 1 As shown in (b), the permanent magnet 14 is formed in a plate shape and has six surfaces: a pair of end faces 14a, 14a, two narrow faces 14b, 14b, and a pair of wide faces 14c, 14c. In this embodiment, one side of the wide face 14c of the permanent magnet 14 is magnetized as the N pole, and the other side of the wide face 14c is magnetized as the S pole. The pair of wide faces 14c, 14c become the surfaces that form magnetic poles. The wide faces 14c, 14c of the permanent magnet 14 are the surfaces through which magnetic flux J1 (J) passes, forming a magnetic flux J2 (J) around one wide face 14c and the other wide face 14c.

[0023] Furthermore, the surface of the permanent magnet 14 in this invention consists of a pair of narrow surfaces 14b, 14b and a pair of wide surfaces 14c, 14c. In the following description, when these are collectively referred to, they are referred to as surface 14f of the permanent magnet 14. Additionally, in the following description, the wall surface opposite each narrow surface 14b in the wall surface forming the groove 13 described later is referred to as wall surface 13b, and the wall surface opposite each wide surface 14c in the wall surface forming the groove 13 described later is referred to as wall surface 13c. Furthermore, these wall surfaces 13b and 13c are referred to as wall surface 13f of the groove 13.

[0024] Figure 2 yes Figure 1 (a) is a top view of the rotor core. Figure 2 As shown, in this embodiment, each slot 13 is rectangular when viewed from above, and two adjacent slots 13 are arranged side by side when viewed from above. These are formed at 90° intervals around the rotation axis (central axis CL). A permanent magnet 14 is inserted into each of two adjacent slots 13 to form a magnetic field. Therefore, in the rotor core 10, eight permanent magnets 14 are inserted into the eight slots 13, 13... as a whole, thereby forming four magnetic poles on the outer periphery of the rotor core 10.

[0025] Figure 3 (a) is along Figure 2 A sectional view cut along line AA. Figure 3 (b) is along Figure 2 A sectional view cut along the BB line. For example... Figure 3 As shown in (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 longitudinal width (thickness) T2, transverse width W2, and length L2. The thickness T1 of the permanent magnet 14 is less than the longitudinal width T2 of the slot 13. Furthermore, the width W1 of the permanent magnet 14 is less than the transverse width W2 of the slot 13. Additionally, the length L1 of the permanent magnet 14 is the same as the length L2 of the slot 13.

[0026] Thus, a gap D is formed between the surface 14f of the permanent magnet 14 and the wall 13f of the groove 13. Specifically, as Figure 3 As shown in (a), the narrow face 14b of the permanent magnet 14 and the wall face 13b of the slot 13 are opposing planes, and a gap D1 is formed between the narrow face 14b of the permanent magnet 14 and the wall face 13b of the slot 13. Furthermore, as... Figure 3 (b) Figure 4 As shown, 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.

[0027] In this embodiment, magnetic fluid 16 is filled in the gap D between the surface 14f of the permanent magnet 14 and the wall 13f of the groove 13. In this embodiment, magnetic fluid 16 is filled in the gaps D1 and D2 between the narrow face 14b of the permanent magnet 14 and the wall 13b of the groove 13 and between the wide face 14c of the permanent magnet 14 and the wall 13c of the groove 13.

[0028] When filling with magnetic fluid 16, magnetic fluid 16 is applied to both the wide surfaces 14c, 14c and the narrow surfaces 14b, 14b of the permanent magnet. Furthermore, by allowing magnetic fluid 16 to flow into the groove 13 of the rotor core 10, magnetic fluid 16 adheres to the wall surfaces 13f (13b, 13c). In this state, a permanent magnet 14 is inserted through one opening of the groove 13. Thus, each permanent magnet 14 can be embedded in the rotor core 10 while the magnetic fluid 16 is filling the gap D between the surface 14f of the permanent magnet 14 and the wall surface 13f forming the groove 13. Alternatively, while the rotor core 10 is immersed in the groove containing magnetic fluid 16, the magnetic fluid 16 can be filled into the gap D by inserting a permanent magnet 14 into the groove 13.

[0029] The magnetic fluid 16 is a functional fluid with the following properties: it is magnetic as a fluid, and has the property of being attracted by a permanent magnet 14, like iron filings. In this embodiment, the magnetic fluid 16 is a fluid in which magnetic particles (magnetic microparticles) are dispersed in a dispersion medium. To improve the dispersibility of the magnetic particles in the dispersion medium, a surfactant may be attached to the surface of the magnetic particles.

[0030] Examples of materials that constitute the magnetic particles of the magnetic fluid 16 include iron, nickel, cobalt, iron carbonyl, 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, they can be strongly magnetic particles (strong magnetic microparticles) such as magnetite or manganese-zinc ferrite, or soft magnetic particles (soft magnetic microparticles) such as low-carbon steel.

[0031] In particular, strongly magnetic particles such as magnetite are not easily affected by the magnetic field generated by the permanent magnet 14 because magnetite is a strongly magnetic material. Moreover, since magnetite is an iron oxide, it is easy to ensure the electrical insulation between the permanent magnet 14 and the rotor core 10. In addition, the strongly magnetic particles are also adsorbed on the wall surface 13f of the groove 13. Therefore, it is easy to retain the magnetic fluid 16 when filling the gap D between the surface 14f of the permanent magnet 14 and the wall surface 13f of the groove 13.

[0032] Examples of dispersion media constituting the magnetic fluid 16 include ester oils such as polyol esters, diesters, and complex esters; hydrocarbon oils such as isoalkanes, polyalphaolefins, alkylnaphthalenes, and polyethers; or silicone oils (fluorinated oils) such as dimethyl silicone, modified silicone, and diethyl silicone.

[0033] In these applications, insulating oil is preferred as the dispersing medium. This allows for the suppression of eddy current circuits between the permanent magnet 14 and the rotor core 10 when driving a rotary motor, thereby preventing a decrease in the output efficiency of the rotary motor.

[0034] The resistivity ρ of the dispersion medium is preferably in the range of 10¹⁰ to 10¹⁸ Ω·m. A higher resistivity ρ is better, with 10¹⁸ Ω·m being the upper limit for resistivity ρ, which represents the value of the insulating oil that satisfies the following characteristics of the dispersion medium. If the resistivity ρ of the dispersion medium is lower than the lower limit of 10¹⁰ Ω·m, the permanent magnet 14 becomes conductive with the electromagnet plate, generating an eddy current circuit between the magnet and the electromagnet plate, which may lead to increased losses in the rotating motor (reduced output efficiency of the rotating motor).

[0035] Furthermore, the relative permeability μr of the dispersion medium is preferably in the range of 1 to 2. This reduces the flow impairment of the magnetic flux through the permanent magnet 14 via the magnetic fluid. Here, a higher relative permeability μr is better, and the upper limit of μr, i.e., 2, is the value of the dispersion medium that can be manufactured by conventional methods. If the relative permeability μr of the dispersion medium is lower than the lower limit of 1, similar to the situation where air or resin is present in the gap D between the surface 14f of the permanent magnet 14 and the wall 13f of the forming groove 13, a decrease in the output of the rotary motor may occur.

[0036] Furthermore, the boiling point of the dispersion medium is preferably in the range of 160 to 400°C. This prevents evaporation of the dispersion medium even when the rotor 1 is heated while driving the rotary motor. Here, a higher boiling point of the dispersion medium is preferable; 400°C, the upper limit of the boiling point, represents a value suitable for dispersion media that can be manufactured using conventional methods. If the boiling point of the dispersion medium is lower than the lower limit of 160°C, the dispersion medium may evaporate (vaporize) when the rotor 1 is heated while driving the rotary motor. This could potentially prevent the permanent magnet 14 from being held in place by the magnetic fluid 16 within the rotor core 10.

[0037] Examples of dispersion media with these properties include isoalkanes (resistivity ρ: 10¹² Ω·m, relative permeability μr: 1, boiling point: 160 °C), alkylnaphthalenes (resistivity ρ: 10¹⁰ Ω·m, relative permeability μr: 1, boiling point: 400 °C), polyalphaolefins (resistivity ρ: 10¹² Ω·m, relative permeability μr: 1, boiling point: 300 °C), or fluorinated oils (resistivity ρ: 10¹⁸ Ω·m, relative permeability μr: 2, boiling point: 200 °C).

[0038] According to this embodiment, such as Figure 4 As shown, a magnetic fluid 16 is filled in the gap D between the surface 14f of the permanent magnet 14 and the wall 13f of the groove 13, so that the permanent magnet 14 can be fixed to the rotor core 10 by the magnetic force (magnetic flux J) of the permanent magnet 14 through the magnetic fluid 16.

[0039] By using insulating oil in the dispersion medium of the magnetic fluid 16, conduction between the permanent magnet 14 and the rotor core 10 can be suppressed when driving the rotating electric motor, thus forming eddy current circuit C1 only in the permanent magnet 14. Therefore, the formation of eddy current circuit C2 between the permanent magnet 14 and the rotor core 10 can be prevented. As a result, the reduction in the output efficiency of the rotating electric motor can be suppressed.

[0040] 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 in the stacking direction. Therefore, compared to the conventional method of fixing the permanent magnet to the rotor core using resin material, the permanent magnet 14 can be easily removed from the slot 13 of the rotor core 10. The permanent magnet 14 can be recycled simply by wiping the surface 14f of the removed permanent magnet 14 with the magnetic fluid, thus improving its recyclability.

[0041] The above describes one embodiment of the present invention in detail, but the present invention is not limited to the described embodiment, and various design changes can be made without departing from the spirit of the present invention as set forth in the claims.

[0042] Symbol Explanation

[0043] 1-Rotor of a rotating electric motor, 10-Rotor core, 10a-Steel plate, 11-Through hole, 12-Rotating shaft, 13-Slot, 13f-Wall, 14-Permanent magnet, 14b-Narrow face, 14c-Wide face (surface), 16-Magnetic fluid, CL-Central shaft.

Claims

1. A rotor for a rotary electric motor, comprising: a rotor core formed by stacking multiple circular steel plates and having multiple slots extending through the stacking 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, characterized in that... A gap is formed between the surface of the permanent magnet and the wall forming the groove. The gap is filled with magnetic fluid.

2. The rotor of the rotary electric motor according to claim 1, characterized in that, The magnetic fluid is a magnetic fluid that disperses magnetic particles in insulating oil.

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