The rotor and motor are assembled together with the rotor.

Abstract

[Problem] To provide a rotor provided with an insulation member (connection part) that can prevent thermal cracking while maintaining strength. [Solution] A rotor 3 includes an outer peripheral-side iron core 32, an inner peripheral-side iron core 34, and an insulation member (connection part) 33 which connects the outer peripheral-side iron core and the inner peripheral-side iron core and is formed of an insulation resin. A plurality of first recess parts 331, 332 arranged in an annular shape and a plurality of second recess parts 336, 337 connecting the first recess parts 331, 332 adjacent to each other in the circumferential direction are provided on both end surfaces of the insulation member 33 in an axis O direction. The depths of the second recess parts 336, 337 are formed to be shallower than the depths of the first recess parts 331, 332.

Description

Rotor and motor equipped with the rotor

[0001] The present invention relates to a rotor having an insulating member and a motor equipped with the rotor.

[0002] Conventional motors include an inner rotor type permanent magnet motor in which a rotor having permanent magnets is rotatably disposed inside a stator that generates a rotating magnetic field. This permanent magnet motor is used, for example, for rotationally driving a blower fan mounted on an air conditioner.

[0003] When this permanent magnet motor is driven by a PWM inverter that performs high-frequency switching, a potential difference (shaft voltage) is generated between the inner ring and the outer ring of the bearing. When this shaft voltage reaches the breakdown voltage of the oil film inside the bearing, a current flows inside the bearing, causing electrical erosion of the bearing. To prevent this electrical erosion of the bearing, for example, a rotor having an insulating member is known (see, for example, Patent Document 1).

[0004] This rotor includes, for example, an annular permanent magnet, an annular outer peripheral side core located on the inner diameter side of the permanent magnet, an annular inner peripheral side core located on the inner diameter side of the outer peripheral side core, an insulating member located between the outer peripheral side core and the inner peripheral side core, and a shaft fixed to a through hole penetrating in the direction of the central axis of the inner peripheral side core.

[0005] Such an insulating member of the rotor is a connecting portion that connects the outer peripheral side core and the inner peripheral side core, and is formed of, for example, a resin filled between the outer peripheral side core and the inner peripheral side core.

[0006] Japanese Patent Application Laid-Open No. 2010-166689

[0007] Incidentally, when the above-described electrical erosion of the bearing occurs when the permanent magnet motor is driven by a PWM inverter, the neutral point potential of the stator winding does not become zero, and a voltage called a common mode voltage is generated. Since this common mode voltage includes high-frequency components due to switching, a shaft voltage is generated between the outer ring and the inner ring of the bearing by the stray capacitance inside the permanent magnet motor.

[0008] The common-mode voltage is divided into potentials on the inner ring side (shaft side) of the bearing due to the capacitance distribution between the stator windings and the shaft, and the capacitance between the shaft and the inverter drive circuit board. The common-mode voltage is then divided into potentials on the outer ring side (bracket side) of the bearing due to the capacitance between the stator windings and the bracket, and the capacitance between the bracket and the inverter drive circuit board. The potential difference between the inner and outer ring sides of the bearing becomes the shaft voltage.

[0009] When the upper limit of the thickness of the rotor's insulating material is structurally restricted, and even when an insulating resin (e.g., PBT resin) is used as the material, the impedance on the rotor side (bearing inner ring side) is low and the shaft voltage is high, the prior art described in Patent Document 1 is designed to suppress the shaft voltage by forming an air layer or voids in a part of the insulating material. The relative permittivity of air is approximately 1, which is lower than that of PBT, which has a relative permittivity of about 3 (i.e., air has higher insulating properties than insulating resin). Therefore, by providing an air layer or voids, it is possible to reduce the capacitance of the rotor and increase the impedance on the rotor side (bearing inner ring side).

[0010] However, when numerous voids are formed in the insulating member to create an air layer, as described in Patent Document 1, there was a risk of reducing the strength of the insulating member. On the other hand, thermal stress is generated in the insulating member due to the operating environment of the permanent magnet motor and the heat generated from the stator windings during operation. If thermal stress is concentrated in a part of the insulating member, there is a concern that the durability of the insulating member will decrease and cracks or fissures may occur. It was also desired to alleviate this thermal stress.

[0011] Therefore, the present invention aims to provide a rotor having an insulating member that can prevent thermal cracking while maintaining strength, and an electric motor equipped with the rotor.

[0012] To solve the above problems, one embodiment of the rotor of the present invention comprises an outer circumferential core, an inner circumferential core, and a connecting portion that connects the outer circumferential core and the inner circumferential core. The connecting portion is made of an insulating resin. The axial end faces of the connecting portion are provided with a plurality of annularly arranged first recesses and a plurality of second recesses that connect adjacent first recesses in the circumferential direction. The depth of the second recesses is formed to be shallower than the depth of the first recesses.

[0013] One embodiment of the electric motor of the present invention comprises a stator fixed to the motor casing and a rotor disposed on the inner diameter side of the stator. The rotor comprises an annular outer core on which permanent magnets are fixed, an inner core located on the inner diameter side of the outer core, a connecting portion located between the outer and inner cores and made of insulating resin, and a shaft connected to the inner core and rotatably supported by bearings on the motor casing. The rotor is provided with a plurality of annularly arranged first recesses and a plurality of second recesses connecting adjacent first recesses in the circumferential direction on both axial end faces of the connecting portion. The depth of the second recesses is formed to be shallower than the depth of the first recesses.

[0014] According to the present invention, it is possible to prevent thermal cracking while maintaining the strength of the connecting portion formed of an insulating resin.

[0015] This is a longitudinal cross-sectional view showing the permanent magnet motor according to the present invention. These are perspective views (a) and plan views (b) of the outer circumference core of the rotor of the permanent magnet motor according to the present invention. These are perspective views (a) and plan views (b) of the inner circumference core of the rotor of the permanent magnet motor according to the present invention. These are perspective views (a) and plan views (b) of the insulating member in the rotor of the permanent magnet motor according to the present invention. This is a perspective view of the rotor of the permanent magnet motor according to the present invention. This is a plan view of the rotor of Figure 5. This is a cross-sectional view taken along line A-A in Figure 6. This is a cross-sectional view taken along line B-B in Figure 6. This is a cross-sectional view taken along line C-C in Figure 7. This is a cross-sectional view taken along line D-D in Figure 7. This is a perspective view of the rotor, shaft and second bearing of the permanent magnet motor according to the present invention. This is a transverse cross-sectional view showing the permanent magnet motor according to the present invention. This is a perspective view showing the permanent magnet motor of Figure 1 or Figure 12 being attached to the outdoor unit of an air conditioner. This is a partial enlarged view of the left side of Figure 1.

[0016] Next, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, identical or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and do not necessarily correspond to the actual parts. Therefore, the specific components should be determined by referring to the following description.

[0017] Furthermore, the embodiments described below illustrate devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the shape, structure, arrangement, etc. of the components to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims described in the patent claims.

[0018] The following describes an electric motor according to one embodiment of the present invention.

[0019] <Overall Configuration of the Electric Motor> Figures 1 to 12 illustrate the configuration of the electric motor 1 in the first embodiment. As shown in these figures, this permanent magnet electric motor 1 is, for example, a brushless DC motor. This electric motor 1 is used to rotate a blower fan mounted on the outdoor unit 10 of an air conditioner, as shown in Figure 13. The outdoor unit 10 of the air conditioner includes, for example, a bottom plate 102 that is screwed to the base 101 of the outdoor unit 10, a top plate 103 that is fixed to the top of the outdoor unit 10, a base 104 to which the electric motor 1 is attached, and two support columns 105 to which the bottom plate 102, top plate 103, and base 104 are fixed. The electric motor 1 is screwed to the center of the base 104.

[0020] In the following description, we will use an inner rotor type permanent magnet motor 1 as an example, in which a rotor 3 having permanent magnets 31 is rotatably arranged on the inner circumference side of a stator 2 that generates a rotating magnetic field. The permanent magnet motor 1 in this embodiment comprises a stator 2, a rotor 3, and a motor casing 6.

[0021] <Stator and Rotor> The stator 2 comprises a stator core 21 having a cylindrical yoke and multiple teeth extending inward from the yoke, and a winding 23 wound around the teeth via an insulator 22. The stator 2 is covered by a motor casing 6 made of resin, except for the inner circumferential surface of the stator core 21.

[0022] The rotor 3 is rotatably positioned on the inner circumference side of the stator core 21 of the stator 2 with a predetermined gap. This rotor 3 is a surface magnet type, with permanent magnets 31 arranged in an annular pattern on its outer circumference facing the stator core 21. The permanent magnets 31 are fixed to the outer circumference surface of the outer circumference core 32, which will be described later. This shaft 35 is connected to the inner circumference core 34, and the power generated by the rotor 2 is transmitted to the load (blower fan) via the shaft 35, thereby rotating the blower fan. The shaft 35 is supported by a first bearing 41 and a second bearing 42, with the first bearing 41 supported by a first bracket 51 and the second bearing 42 supported by a second bracket 52, thereby supporting the rotor 3 so that it can rotate freely.

[0023] <Bearings and Brackets> The first bearing 41 supports one end (output side) of the rotor shaft 35. The second bearing 42 supports the other end (non-output side) of the rotor shaft 35. For example, ball bearings are used for the first bearing 41 and the second bearing 42.

[0024] The first bracket 51 is made of metal (such as steel plate or aluminum) and is positioned on one end of the motor housing 6, that is, on the output side of the shaft 35. The first bracket 51 has a first bearing housing portion 511 for housing the first bearing 41 and a flange portion 512 that extends outward from the open end of the first bearing housing portion 511. The first bearing housing portion 511 is formed in a cylindrical shape with a bottom portion having a through hole for the shaft 35 to pass through, and the flange portion 512 of the first bracket 51 is insert-molded during the molding of the motor housing 6 and is integrated with the motor housing 6.

[0025] The outer ring of the first bearing 41 is press-fitted into the inner surface of the first bearing housing 511, and the output side of the shaft 35, which is supported by the inner ring of the first bearing 41, protrudes outward from a through hole formed in the center of the bottom of the first bearing housing 511.

[0026] The second bracket 52 is made of metal (such as steel plate or aluminum) and is fixed to the other end of the motor housing 6, that is, the side opposite the output of the shaft 35. The second bracket 52 has a disc-shaped bracket body portion 521, an outer edge portion 520 that closes the end of the motor housing 6 on the side opposite the output, and a second bearing housing portion 522 for housing the second bearing 42.

[0027] The second bracket 52 has its outer edge 520 screwed to the end of the motor casing 6 that is not on the output side. The second bearing housing 522 is formed in the center of the bracket body 521 as a hole with a circular bottom surface recessed from the motor casing 6 side (output side).

[0028] The first bearing 41 is housed in a first bearing housing 511 provided on the first bracket 51, and the second bearing 42 is housed in a second bearing housing 522 provided on the second bracket 52. The first bearing 41 and the first bearing housing 511, and the second bearing 42 and the second bearing housing 522 are electrically connected.

[0029] The second bracket 52 integrally includes a heat sink between the second bearing housing portion 522 and the outer edge portion 520 in the radial direction. This makes it possible to save space in the electric motor 1. The second bracket has heat dissipation fins 523 erected outward on the side of the shaft 35 that is not output, and heat from the circuit board 72 (particularly the electronic components 721 mounted on the circuit board 72) for controlling the electric motor 1 is efficiently dissipated by the heat dissipation fins 523 via the heat transfer member 71.

[0030] <Structure, Operation, and Effects of the Rotor According to the Present Invention> Next, the structure, operation, and effects of the rotor 3 according to the present invention will be described using Figures 2 to 10 in the permanent magnet motor 1 of this embodiment. In the permanent magnet motor 1, an insulating member 33 is provided in a part of the rotor 3, as shown in Figure 1, in order to prevent electrolytic corrosion from occurring in the first bearing 41 and the second bearing 42. The specific configuration of the rotor 3 will be described below.

[0031] As shown in Figures 1 to 11, the rotor 3 comprises a permanent magnet 31, an outer circumference core 32, an insulating member (connecting part) 33, an inner circumference core 34, and a shaft 35, arranged from the outer diameter side to the inner diameter side.

[0032] As shown in Figures 1, 11 and 12, the permanent magnet 31 is formed in a ring shape from a plurality of (for example, 8 or 10) permanent magnet pieces 311 such that the north pole and south pole alternate at equal intervals in the circumferential direction. Alternatively, the permanent magnet 31 may be a plastic magnet formed in a ring shape by solidifying magnetic powder with resin.

[0033] As shown in Figure 2, the outer core 32 is formed in an annular shape and is located on the inner diameter side of the permanent magnet 31, as shown in Figures 11 and 12. The outer core 32 is provided with a plurality of inner circumferential recesses 321 (for example, five in the circumferential direction) that are recessed from the inner circumferential surface (see Figure 2) toward the outer diameter side and extend in the direction of the axis O of the rotor 3 (hereinafter, the axial direction), in order to ensure a function of preventing rotation with respect to the insulating member 33, which will be described later. That is, the inner circumferential recesses 321 function as keyways (grooves that prevent slippage between rotating members. Keyways improve the fastening force between members and can increase the power transmission efficiency) that prevent rotation with respect to the insulating member 33. Furthermore, the outer core 32 is provided with a plurality of outer circumferential protrusions 322 (for example, ten in the circumferential direction) that project from the outer circumferential surface toward the outer diameter side in order to position the permanent magnet 31.

[0034] Multiple inner circumferential recesses 321 extend axially from the end face of the insulating member 33 and are arranged at equal intervals in the circumferential direction. In this embodiment, two inner circumferential recesses 321 are arranged so as to extend axially from both ends of the outer circumferential core 32. As a result, the outer circumferential core 32 has partition walls 323 (retaining parts) between axially adjacent inner circumferential recesses 321, and these partition walls 323 can prevent the insulating member 33 (connecting part) from coming loose (in both axial directions).

[0035] The multiple outer peripheral protrusions 322 each extend in the axial direction and are arranged at equal intervals in the circumferential direction. Furthermore, each outer peripheral protrusion 322 is positioned to extend in the axial direction from one end to the other of the outer peripheral core 32.

[0036] As shown in Figure 3, the inner core 34 is formed in an annular shape and is located on the inner diameter side of the outer core 32, as shown in Figures 5 to 10. The inner core 34 is provided with a plurality of outer recesses 341 (for example, six in the circumferential direction) that are recessed inward from the outer surface (see Figure 3) and extend axially, in order to ensure a function of preventing rotation with respect to the insulating member 33, which will be described later. In other words, the outer recesses 341 function as keyways that prevent rotation with respect to the insulating member 33.

[0037] Multiple outer peripheral recesses 341 extend in the axial direction and are arranged at equal intervals in the circumferential direction. In this embodiment, the outer peripheral recesses 341 are separated by partition walls 344 (retaining parts) located in the axial center. Therefore, two outer peripheral recesses 341 are arranged so as to extend from both ends of the inner circumferential core 34. As a result, partition walls 344 exist between axially adjacent outer peripheral recesses 341 of the inner circumferential core 34, and these partition walls 344 (retaining parts) can prevent the insulating member 33 (connecting part) from coming loose (in both axial directions).

[0038] Furthermore, the inner core 34 has a through hole 343 that penetrates axially at its center. A shaft 35 is passed through the through hole 343 of the inner core 34, connecting the shaft 35 to the inner core 34. The inner core 34 may also have a plurality of through holes 342 for weight reduction between the through hole 343 and the outer surface of the inner core 34. These plurality of through holes 342 are arranged at equal intervals in the circumferential direction so that, when viewed from the axial direction, the shape of the inner core 34 in which the through holes 342 are formed becomes spoke-like.

[0039] The insulating member 33 is made of a dielectric resin such as PBT (polybutylene terephthalate) or PET (polyethylene terephthalate) and is located between the outer core 32 and the inner core 34. The insulating member 33 is integrally molded with the outer core 32 and the inner core 34 by insert molding, in which resin is filled between the outer core 32 and the inner core 34. This insulating member 33 reduces the capacitance between the outer core 32 and the inner core 34 (part of the capacitance between the windings 23 of the stator 2 and the shaft 35), thereby lowering the potential on the inner ring side of the first bearing 41 and the second bearing 42, and adjusting to reduce the potential difference between the inner ring side and the outer ring side.

[0040] As shown in Figure 4, the insulating member 33 has (multiple) outer circumferential protrusions 338 on its outer circumferential surface that engage with the inner circumferential recess 321 of the outer circumferential core 32 described above. The insulating member 33 also has (multiple) inner circumferential protrusions 339 on its inner circumferential surface that engage with the outer circumferential recess 341 of the inner circumferential core 34.

[0041] Here, the engagement portion (inner circumference recess 321 and outer circumference protrusion 338) provided between the outer circumference core 32 and the insulating member (connecting portion) 33 to prevent rotation between the outer circumference core 32 and the insulating member 33 is referred to as the first concave-concave engagement portion, and the engagement portion (inner circumference protrusion 339 and outer circumference recess 341) provided between the insulating member 33 and the inner circumference core 34 to prevent rotation between the insulating member 33 and the inner circumference core 34 is referred to as the second concave-concave engagement portion. As described above, in this embodiment, the concave portions of the concave-concave engagement portion (first concave-concave engagement portion and second concave-concave engagement portion) are formed on the outer circumference core 32 and the inner circumference core 34, and the protrusion portion of the concave-concave engagement portion is formed on the insulating member (connecting portion) 33 is shown as an example.

[0042] Furthermore, the arrangement of the recessed and convex portions of the interlocking engagement portion on either the rotor core (32, 34) or the insulating member 33 may be reversed from the case described above. For example, the convex portions of the interlocking engagement portion may be provided on the outer circumferential core 32 and the inner circumferential core 34, and the recessed portions of the interlocking engagement portion may be provided on the insulating member 33.

[0043] As shown in Figures 2-4 and 7-8, the first interlocking parts 321, 338 and the second interlocking parts 339, 341 have partition walls 323 (retaining parts) formed between adjacent inner circumferential recesses 321 in the axial direction, and partition walls 344 (retaining parts) formed between adjacent outer circumferential recesses 341 in the axial direction. Therefore, the insulating member 33 can be prevented from coming off the outer core 32 and the inner core 34. Thus, as described above, the first interlocking parts 321, 338 and the second interlocking parts 339, 341 can have both rotation-preventing and detachment-preventing functions through the engagement of their respective interlocking parts.

[0044] Here, consider the shear stress received by the concavo-convex engagement part that functions as a key (mechanical element for fastening around the rotating body) when the rotor 3 rotates. In a shaft transmitting torque with a magnitude of T [N·m], assuming that the position where the concavo-convex engagement part (key) is arranged is at a radius r [m] from the central axis O, when assuming that the shape of the concavo-convex engagement part is uniform, the shear stress τ [Pa] acting on the concavo-convex engagement part can be expressed as τ = α×T / r (α: proportionality constant). Also, comparing the radial position of the first concavo-convex engagement part (that is, the inner diameter of the outer peripheral side core 32) r1 provided between the outer peripheral side core 32 and the insulating member 33, and the radial position of the second concavo-convex engagement part (that is, the outer diameter of the inner peripheral side core 34) r2 provided between the insulating member 33 and the inner peripheral side core 34, it always holds that r1 > r2. Furthermore, the torque transmitted between the outer peripheral side core 32 and the insulating member 33 and the torque transmitted between the insulating member 33 and the inner peripheral side core 34 can be regarded as equal. Therefore, the shear stress τ2 acting between the members on the inner diameter side (the second concavo-convex engagement part between the inner peripheral side core 34 and the insulating member 33) is always greater than the shear stress τ1 acting between the members on the outer diameter side (the first concavo-convex engagement part between the outer peripheral side core 32 and the insulating member 33) (that is, τ1 < τ2 always holds). Thus, by making the number of the second concavo-convex engagement parts 339 and 341 in the circumferential direction more than the number of the first concavo-convex engagement parts 321 and 338 in the circumferential direction, the shear stress acting on each of the first concavo-convex engagement parts 321 and 338 provided between the members on the inner diameter side can be reduced, and the anti-rotation of the insulating member 33 can be made more robust.

[0045] The shaft 35 is passed through the through hole 343 provided in the inner peripheral side core 34 and fixed to the inner peripheral side core 34 by press-fitting or caulking or the like.

[0046] The permanent magnet motor 1 used to rotate the blower fan mounted on the air conditioner is driven by a PWM inverter, so the neutral point potential of the windings does not become zero, and a voltage called common mode voltage is generated. Due to this common mode voltage, a potential difference (shaft voltage) is generated between the outer ring and inner ring of the first bearing 41 and the second bearing 42 due to the stray capacitance inside the permanent magnet motor 1. When this shaft voltage reaches the dielectric breakdown voltage of the oil film inside the bearing, current flows inside the bearing, causing electrolytic corrosion inside the bearing.

[0047] In the rotor 3 described above, the insulating member 33 is formed in a cylindrical shape, as shown in Figures 4 to 10. To reduce the capacitance of the rotor 3, a first axial hole 331 is formed at one end in the axial direction, and a second axial hole 332 is formed at the other end in the axial direction to similarly reduce the capacitance of the rotor 3. Multiple (for example, 10) of these first axial holes 331 and second axial holes 332 are formed at equal intervals in the circumferential direction. Partition walls 334 are uniformly formed between each of the multiple first axial holes 331 and between each of the multiple second axial holes 332, separating adjacent first axial holes 331 and adjacent second axial holes 332 in the circumferential direction. Here, the plan view and bottom view of the rotor 3 are the same. The partition walls 334 increase the mechanical strength of the insulating member 33 (connecting part), and when the rotor 3 rotates, the power of rotational motion can be sufficiently transmitted between the inner core 34 and the outer core 32.

[0048] Further, as shown in FIG. 7, the first axial hole 331 and the second axial hole 332 face each other in the axial direction, and a partition wall portion 333 is provided at the axial center of the insulating member 33 (between the first axial hole 331 and the second axial hole 332 that face each other in the axial direction) so that the depths of the holes are the same. The partition wall portion 333 enhances the mechanical strength of the insulating member 33 (connecting portion), and when the rotor 3 rotates, the power of the rotational movement can be sufficiently transmitted between the inner peripheral side core 34 and the outer peripheral side core 32. Further, by providing this partition wall portion 333, the bottom portion 335c of the first axial hole 331 is formed on one end side of the partition wall portion 333, and the bottom portion 335c of the second axial hole 332 is formed on the other end side of the partition wall portion 333. Then, side walls 335a and 335b are formed along the axial direction from the bottom portions 335c of the first axial hole 331 and the second axial hole 332, respectively.

[0049] Thus, the first axial hole 331 and the second axial hole 332 have a structure with depth in the direction along the axial direction from both end faces due to the formation of the partition wall portion 333. Further, as shown in FIGS. 6 to 9, the end face shapes of the first axial hole 331 and the second axial hole 332 as viewed from the axial direction are formed in an arc shape along the circumferential direction, and a plurality of them (for example, 10 in the circumferential direction) are formed at equal intervals.

[0050] Here, for example, when forming the first axial hole 331 and the second axial hole 332 in the rotor 3 with a small radius and a large axial thickness, since the radius of the rotor 3 is small, the radial length (width) R of the first axial hole 331 and the second axial hole 332 is also limited to be small.

[0051] Further, since the insulating member 33 in the present embodiment is formed by integrally molding a dielectric resin such as PBT or PET together with the outer peripheral side core 32 and the inner peripheral side core 34, considering the draft of the mold during molding of the first axial hole 331 and the second axial hole 332, the radial length (width) R of the first axial hole 331 and the second axial hole 332 cannot be increased.

[0052] To reduce the capacitance of such a rotor 3, one might consider increasing the depth of the first axial hole 331 and the second axial hole 332. However, if the depth of the first axial hole 331 and the second axial hole 332 is made too deep, the thickness of the wall portion 333 separating the first axial hole 331 and the second axial hole 332 will become thinner, reducing the mechanical strength of the insulating member 33. Therefore, a wall portion 333 of an appropriate thickness is necessary to ensure mechanical strength. Here, in order to increase mechanical strength, the axial thickness of the partition wall 323 (retaining portion) of the outer core 32 and the axial thickness of the partition wall 344 (retaining portion) of the inner core 34 are made approximately equal to the (axial) thickness of the wall portion 333.

[0053] Furthermore, in this embodiment, as described above, the first axial hole 331 and the second axial hole 332 are formed in an arc shape along the circumferential direction when viewed from the axial direction, as shown in Figures 6 to 9. That is, by making the radial length (width) R of the first axial hole 331 and the second axial hole 332 constant in the circumferential direction, the size of the holes can be increased within a limited space, and the capacitance of the rotor 3 can be reduced.

[0054] As described above, the size and shape of the first axial hole 331 and the second axial hole 332 are determined considering both the reduction of the capacitance of the rotor 3 and the securing of mechanical strength.

[0055] Incidentally, generally speaking, the coefficient of linear expansion of resin is more than 10 times larger than that of metal. Therefore, the amount of expansion of the resin insulating member 33 when the temperature rises and the amount of contraction when the temperature falls are larger compared to the metal outer core 32 and inner core 34.

[0056] As shown in Figures 6 to 8, the insulating member 33 has side walls 335a and 335b that are thinner in the radial direction and thicker in the axial direction. Therefore, the amount of expansion and contraction of the side walls 335a and 335b in the insulating member 33 is greater in the axial direction than in the radial direction.

[0057] Furthermore, the expansion and contraction of the wall portion 333 and partition wall 334 of the insulating member 33 can be divided into radial and axial components. However, since radial expansion and contraction are restricted by the outer core 32 and inner core 34, the axial expansion and contraction tend to be larger than the radial expansion and contraction.

[0058] Here, as shown in Figures 7 and 8, the insulating member 33 sandwiched between the outer core 32 and the inner core 34 experiences axial displacement (change in position) due to expansion and contraction, which varies depending on its position in the axial direction before expansion or contraction. That is, the insulating member 33 expands or contracts in both axial directions, with the axial central portion as the boundary, so the displacement is greater the further away the insulating member 33 is from the axial central portion. For example, the axial central portion (near the wall portion 333) experiences almost no axial displacement before and after expansion. On the other hand, the axial end (near the end portion 335d) experiences large axial displacement before and after expansion. Note that the insulating member 33 has a small radial width and its radial expansion and contraction are restricted, so the radial displacement due to expansion and contraction remains almost unchanged regardless of its axial position.

[0059] Furthermore, thermal stress tends to concentrate in the insulating member 33 where radial expansion and contraction are restricted by the outer core 32 and the inner core 34. Therefore, in this embodiment, thermal stress concentrates in the wall portion 333 and the partition wall 334 of the insulating member 33.

[0060] Thus, when considering the expansion of the side walls 335a, 335b, wall portion 333, and partition wall 334 of the insulating member 33 due to temperature rise, the amount of axial expansion tends to be larger than the amount of radial expansion, and thermal stress is particularly concentrated in areas where expansion is restricted or where the amount of displacement is large.

[0061] Furthermore, due to the expansion of the insulating member 33, thermal stress concentrates at the point where the wall portion 333 and the side walls 335a and 335b intersect, as shown in Figure 7. However, because the first axial hole 331 and the second axial hole 332 (first recess) are provided, the force can be released towards the first recess, thereby mitigating the thermal stress. In addition, due to the expansion of the insulating member 33, thermal stress concentrates at the axial ends of the side walls 335a and 335b. However, because the first recess described above is provided, the force can be released towards the first recess, thereby mitigating the thermal stress.

[0062] On the other hand, the partition wall 334 shown in Figure 8 is restricted from radial expansion by the outer core 32 and the inner core 34, and the displacement due to expansion near the axial end 335d is particularly large. Therefore, due to the effect of the expansion of the insulating member 33, the area near the axial end 335d of the insulating member 33, which covers the inner and outer edges of the outer core 32 and the inner core 34, is particularly prone to cracking.

[0063] Therefore, in order to prevent the thermal cracking described above, the insulating member 33 is configured such that, as shown in Figures 6 and 8, a third axial hole 336 is formed at one end in the axial direction at a position between the annularly arranged first axial holes 331 and between the second axial holes 332, and a fourth axial hole 337 is similarly formed at the other end in the axial direction. These third axial holes 336 and fourth axial holes 337 (second recesses 336 and 337) are formed on the same circumference as the first axial holes 331 and second axial holes 332 (first recesses 331 and 332) and are arranged in an annular shape. Furthermore, the third axial holes 336 and fourth axial holes 337 (second recesses) are formed in multiples (for example, 10) at equal intervals in the circumferential direction, similar to the first axial holes 331 and second axial holes 332. In addition, each of the third axial holes 336 and fourth axial holes 337 is arranged to overlap the partition wall 334 in the axial direction. Furthermore, as shown in Figures 6 to 9, the end face shape of the third axial hole 336 and the fourth axial hole 337, when viewed from the axial direction, is formed in an arc shape along the circumferential direction. In addition, the third axial hole 336 and the fourth axial hole 337 are continuous with the first axial hole 331 and the second axial hole 332, so that annular grooves are formed on both axial end faces of the insulating member 33. That is, when the first axial hole 331 and the second axial hole 332 are considered the first recesses, and the third axial hole 336 and the fourth axial hole 337 are considered the second recesses, annular grooves (331, 336, and 332, 337) are formed annularly on both axial end faces of the insulating member (connecting part) 33. By making the radial length (width) R of these annular grooves constant in the circumferential direction, the force can be uniformly distributed in the circumferential direction.

[0064] In particular, it has been confirmed that when the bottom of the second recess (third axial hole 336, fourth axial hole 337) (position of the axial end of the partition wall 334) is formed to be axially closer to the center than the axial end faces of the rotor core (outer core 32 and inner core 34), the concentration of thermal stress in the insulating member 33 is suppressed. Based on this, in this embodiment, the depths of the third axial hole 336 and the fourth axial hole 337 are formed to a depth of 5.5 mm from the axial end faces of the insulating member 33. On the other hand, the depths of the first axial hole 331 and the second axial hole 332 are formed to a depth of 16.5 mm from the axial end faces of the insulating member 33.

[0065] Here, as shown in Figure 14 and Table 1, the depth of the first axial hole 331 and the second axial hole 332 (depth of the first recess) is M [mm], the depth of the third axial hole 336 and the fourth axial hole 337 (depth of the second recess) is S [mm], the axial length (core stacking thickness) of the outer core 32 and the inner core 34 is L [mm], and the axial thickness of the wall portion 333 (central wall thickness) is C [mm]. In this case, the condition for the bottom of the second recess (336, 337) to be on the axial central side of the rotor core (32, 34) is, as can be seen from Figure 14, 2M + C - 2S < L. It is desirable that the rotor 3 be designed to satisfy this condition. That is, by satisfying this condition, thermal cracking of the insulating member 33 can be prevented more reliably. Note that 2M + C is equal to the axial length of the insulating member 33.

[0066]

[0067] Therefore, by forming the second recesses, the third axial hole 336 and the fourth axial hole 337, the region in which the axial length of the insulating member 33 is large can be reduced, thereby decreasing the total volume of the insulating member 33 and reducing the amount of axial expansion and contraction of the insulating member 33. In addition, because the second recesses 336 and 337 are provided, the force applied near the axial end 335d can be released to the second recess side, thereby easing thermal stress and suppressing the concentration of thermal stress. As a result, the decrease in durability due to the concentration of thermal stress in the insulating member 33 can be suppressed, and the occurrence of thermal cracks and other cracks can be suppressed, thus extending the lifespan.

[0068] Specifically, as shown in Figures 5 to 8, these multiple third axial holes 336 (second recesses) are positioned between multiple first axial holes 331 (first recesses) arranged in an annular pattern, and are formed to connect adjacent first axial holes 331 in the circumferential direction. Similarly, multiple fourth axial holes 337 (second recesses) are positioned between multiple second axial holes 332 (first recesses) arranged in an annular pattern, and are formed to connect adjacent second axial holes 332 in the circumferential direction. This makes it possible to suppress the concentration of thermal stress.

[0069] Furthermore, the depths of the third axial hole 336 and the fourth axial hole 337 are smaller (shallower) than the depths of the first axial hole 331 and the second axial hole 332. This allows for the formation of partition walls 334 between adjacent first axial holes 331 and between adjacent second axial holes 332 in the circumferential direction, thereby increasing the strength of the insulating member 33 (connecting portion).

[0070] Furthermore, when the first axial hole 331 and the second axial hole 332 are designated as the first recess, and the third axial hole 336 and the fourth axial hole 337 are designated as the second recess, annular grooves (331, 336, and 332, 337) are formed in an annular shape on both axial end faces of the insulating member (connecting part) 33. This allows the side walls 335a and 335b at the axial ends of the insulating member 33 to expand toward the radially annular grooves, further mitigating the effects of thermal stress and preventing thermal cracking of the insulating member 33.

[0071] The above description explains the case where the insulating member 33 expands due to heat generated in the windings 23 of the stator 2, depending on the operating environment and driving state of the permanent magnet motor 1. In addition, it is possible to alleviate the concentration of thermal stress around the bottom of the first axial hole 331 and the second axial hole 332, and around the ends of the insulating member 33, when the temperature drops due to the operating environment and driving state of the permanent magnet motor 1. In this embodiment, in order to suppress thermal stress, the insulating member 33 is provided with first recesses 331 and 332 and second recesses 336 and 337, reducing the axial thickness (and volume of resin) of the insulating member 33, thereby reducing stress during thermal expansion and contraction, and preventing thermal cracking of the insulating member 33.

[0072] Therefore, by placing an insulating member 33 on the rotor 3 to prevent electrolytic corrosion of the first bearing 41 and second bearing 42 supporting the shaft 35, and by forming a first axial hole 331 and a second axial hole 332, and a third axial hole 336 and a fourth axial hole 337 in the insulating member 33, it is possible to mitigate the concentration of thermal stress that occurs in the insulating member 33, which is a problem when manufacturing a rotor 3 with a small diameter. As a result, it is possible to manufacture a small rotor 3 that increases the impedance between the outer core 32 and the inner core 34 while maintaining the connection strength between them, thereby reducing the capacitance of the rotor 3. Furthermore, the permanent magnet motor 1 equipped with the rotor 3 can also be miniaturized.

[0073] Here, a component (such as resin or metal) for adjusting capacitance or durability may be attached to at least one of the first axial hole 331 and the second axial hole 332, or to at least one of the third axial hole 336 and the fourth axial hole 337.

[0074] Furthermore, in the embodiments described above, the end face shapes of the first axial hole 331 and the second axial hole 332, and the third axial hole 336 and the fourth axial hole 337, when viewed from the axial direction, are described as being formed in an arc shape along the circumferential direction. However, the shape of each axial hole is not limited to this. Also, the number of each of the first axial hole 331 and the second axial hole 332, and the third axial hole 336 and the fourth axial hole 337 is not limited to 10, but can be any number.

[0075] Furthermore, in each of the above embodiments, the first axial hole 331 and the second axial hole 332 are formed in a symmetrical shape with respect to the wall portion 333, but the invention is not limited to this, and the first axial hole 331 and the second axial hole 332 may be formed in an asymmetrical shape with respect to the wall portion 333 (for example, a C shape when viewed from the axial direction). Similarly, the third axial hole 336 and the fourth axial hole 337 may be formed in an asymmetrical shape with respect to the wall portion 333 (for example, a C shape when viewed from the axial direction).

[0076] Furthermore, although the above embodiments described the application of the present invention to a surface-magnet type rotor 3 in which permanent magnets 31 are arranged on the outer surface of the outer core 32, the present invention is not limited to this, and can also be applied to an embedded-magnet type rotor in which slots extending in the axial direction are formed at chord positions on the outer surface of the outer core 32, and permanent magnets are arranged in these slots.

[0077] 1…Permanent magnet motor 2…Stator 10…Outdoor unit 101…Base 102…Bottom plate 103…Top plate 104…Side plate 21…Stator core 22…Insulator 23…Winding 3…Rotor 31…Permanent magnet 311…Permanent magnet piece 32…Outer circumference core 321…Inner circumference recess (first recessed engagement part) 323…Partition wall (retaining part) 33…Insulating member (connecting part) 33a…One end face 33b…Other end face 331…First axial hole (first recess) 332…Second axial hole (first recess) 333…Wall part 334…Partition wall 335a, 335b…Side wall 335c…Bottom part 335d…End part 336…Third axial hole (second recess) 337...Fourth axial hole (second recess) 338...Outer circumference protrusion (first concave-concave engagement part) 339...Inner circumference protrusion (second concave-concave engagement part) 34...Inner circumference core 341...Outer circumference recess (second concave-concave engagement part) 343...Through hole 344...Partition (retaining part) 35...Shaft 41...First bearing 42...Second bearing 51...First bracket 511...First bearing housing 512...Flange part 52...Second bracket 521...Bracket body part 522...Second bearing housing 523...Heat dissipation fin 6...Motor casing 71...Heat transfer member 72...Circuit board O...Central axis

Claims

DEPCT651. A rotor consisting of an outer iron core and an inner iron core and a linkage connecting the outer and inner iron cores. The linkage is molded with an insulating resin at both ends. In the axial direction of the linkage, numerous first concave sections arranged in an annular pattern are fitted, and numerous second concave sections connecting the first concave sections to each other adjacently in the circumferential direction. The depth of the second concave sections is molded shallower than the depth of the first concave section.

2. The rotor specified in claim 1 is a rotor in which the linkage is fitted with numerous bulkheads separating the first concave sections to each other adjacently in the circumferential direction, and these bulkheads are arranged to overlap in the axial direction. 3.

4. One of the rotors specified in Reputation 1-2 is a rotor in which, at both ends of the axial side of such linkage, annular concave grooves are formed due to numerous such first and numerous such second concave grooves.

5. One of the rotors specified in Reputation 1-3 is a rotor in which, together with, a first concave-convex linkage serving to stop rotation between such outer iron shaft and such linkage mounted between such outer iron shaft and such linkage, and a second concave-convex linkage serving to stop rotation between such linkage and such inner iron shaft and such linkage mounted between such linkage and such inner iron shaft.The rotor specified in Reputation 4 is a rotor in which a detachment barrier is formed between the first convex joints adjacent to each other in the axial direction and between the second convex joints adjacent to each other in the axial direction, where at least one of these barriers prevents the connection from detaching from the outer or inner iron core.

6. The rotor specified in Reputation 4 or 5 is a rotor in which the number of second convex joints is greater than the number of first convex joints.

7. Any of the rotors specified in Reputations 1-6 is a rotor in which the insulating resin is polybutylene terephthalate (PBT) or PET (polyethylene terephthalate). 8.A motor assembled with a rotor is a motor consisting of a stator mounted to the motor's outer shell and a rotor positioned on the inner circumference of the stator. The rotor consists of an outer ring-shaped iron core with permanent magnets attached, an inner iron core at the inner surface of the outer core, and resin-molded insulating linkages between the outer and inner cores. A shaft is also connected to the inner core and supported by bearings for free rotation within the motor's outer shell. Numerous ring-shaped first notches are arranged on both ends in the axial direction of the linkages, and numerous second notches connect the first and second notches adjacent to each other in the circumferential direction. The depth of these second notches is shallower than that of the first notch.