Motor

Abstract

This motor comprises a rotor having a rotor core. The rotor core has: a magnet hole; and air gaps provided on both sides of the magnet hole in the circumferential direction via partition walls.

Description

motor

[0001] The present disclosure relates to a motor.

[0002] In the technical field related to motors, there is known a motor such as that disclosed in Patent Document 1. In Patent Document 1, a permanent magnet is disposed in an embedding hole in a rotor core.

[0003] JP 2014-197970 A

[0004] In Patent Document 1, the amount of magnets per pole is increased to increase the magnet torque and further increase the torque by utilizing reluctance torque. However, when the amount of magnets per pole is increased, the voltage induced in the stator winding becomes a distorted waveform containing many harmonics, which may reduce the energy efficiency of the motor.

[0005] An object of the present disclosure is to provide a motor that can improve energy efficiency.

[0006] According to the present disclosure, there is provided a motor including a rotor having a rotor core, the rotor core having a magnet hole and an air gap provided on both sides of the magnet hole in the circumferential direction via a partition wall.

[0007] According to the present disclosure, a motor that can improve energy efficiency can be provided.

[0008] FIG. 1 is a longitudinal sectional view showing a motor device according to an embodiment. FIG. 2 is a plan sectional view showing a motor device according to an embodiment. FIG. 3 is a schematic view of a portion of a rotor according to an embodiment, viewed from above. FIG. 4 is a schematic view of a portion of a rotor according to an embodiment, viewed from above. FIG. 5 is a schematic view of a portion of a rotor according to an embodiment, viewed from above. FIG. 6 is a schematic view of a portion of a rotor according to an embodiment, viewed from above. FIG. 7 is a diagram showing the relationship between cogging torque and torque according to angle θi according to an embodiment. FIG. 8 is a diagram showing the relationship between cogging torque and torque ripple according to angle θo according to an embodiment. FIG. 9 is a diagram showing the relationship between torque according to angle θo according to an embodiment.

[0009] Hereinafter, embodiments will be described with reference to the drawings. The components of the embodiments described below can be combined as appropriate. In addition, some components may not be used.

[0010] In the embodiment, the direction parallel to the rotation axis AX of the rotor 7 will be referred to as the axial direction, the radial direction of the rotation axis AX of the rotor 7 will be referred to as the radial direction, and the direction circumferentially around the rotation axis AX of the rotor 7 will be referred to as the circumferential direction or the rotation direction.

[0011] A position or direction on one side in the axial direction will be referred to as the upper side or the upper direction, as appropriate, and a position or direction on the other side in the axial direction will be referred to as the lower side or the lower direction, as appropriate. In the radial direction, a position or direction close to the rotation axis AX of the rotor 7 will be referred to as the radially inner side or the inner direction, as appropriate, and a position or direction far from the rotation axis AX of the rotor 7 will be referred to as the radially outer side or the outer direction, as appropriate. A position or direction on one side in the circumferential direction will be referred to as the forward side or the forward direction, as appropriate, and a position or direction on the other side in the circumferential direction will be referred to as the reverse side or the reverse direction, as appropriate.

[0012] [Motor Device] Fig. 1 is a longitudinal sectional view showing a motor device 1 according to an embodiment. Fig. 2 is a plan sectional view showing the motor device 1 according to an embodiment. The motor device 1 generates a rotational force for driving a hydraulic pump of, for example, an electric hydraulic excavator, which is a type of construction machine.

[0013] The motor device 1 includes a motor 2 and a motor case 3. The motor 2 includes a rotor 7, a stator 8, and a fixing ring 9. The motor 2 is an inner rotor type. The stator 8 is disposed around the rotor 7. The rotor 7 rotates about a rotation axis AX.

[0014] The rotor 7 includes a rotor core 21 , a permanent magnet 22 , and a rotor shaft 23 .

[0015] The rotor core 21 includes a plurality of stacked steel plates. The steel plates are made of a metal whose main component is iron. The rotor core 21 is disposed to surround the rotation axis AX.

[0016] The permanent magnets 22 are supported by the rotor core 21. The permanent magnets 22 are arranged inside the rotor core 21. A plurality of the permanent magnets 22 are arranged around the rotation axis AX.

[0017] The rotor core 21 has a plurality of magnet holes 24 spaced apart in the circumferential direction. The plurality of magnet holes 24 are spaced apart in the circumferential direction at equal intervals. The magnet holes 24 are arranged so as to penetrate the upper end surface and the lower end surface of the rotor core 21. Permanent magnets 22 are arranged in the magnet holes 24. In the embodiment, the number of magnet holes 24 is 24. In the embodiment, the permanent magnet 22 is divided into a plurality of parts in the axial direction and arranged inside the rotor core 21.

[0018] The rotor shaft 23 extends in the axial direction. The central axis of the rotor shaft 23 coincides with the rotation axis AX. The rotor shaft 23 is disposed inside the rotor core 21. The rotor core 21 and the rotor shaft 23 are fixed together. An upper portion of the rotor shaft 23 protrudes upward from the upper end surface of the rotor core 21. A lower portion of the rotor shaft 23 protrudes downward from the lower end surface of the rotor core 21.

[0019] The stator 8 includes a stator core 13 , an insulator 14 fixed to the stator core 13 , and a coil 15 attached to the stator core 13 via the insulator 14 .

[0020] The stator core 13 is arranged around the rotor core 21. The stator core 13 includes a plurality of stacked steel plates. The steel plates are metal plates whose main component is iron. The stator core 13 has an annular yoke and a plurality of teeth that protrude radially inward from the inner peripheral surface of the yoke. The yoke is arranged to surround the rotation axis AX. A plurality of teeth are arranged circumferentially. The plurality of teeth are arranged at equal intervals circumferentially. A slot is provided between adjacent pairs of teeth.

[0021] The insulator 14 is disposed so as to cover at least a portion of the surface of the stator core 13. The insulator 14 is an electrically insulating member made of synthetic resin. The insulator 14 is fixed to the stator core 13. The stator core 13 and the coils 15 are electrically insulated by the insulator 14. In the embodiment, the insulator 14 is molded by any molding method, such as injection molding, and then attached to the stator core 13.

[0022] The coils 15 are wound around the teeth via the insulators 14. In the embodiment, the coils 15 are wound around the teeth by concentrated winding. A portion of the coils 15 is disposed inside the slots. A portion of the coils 15 protrudes upward from the upper end surface of the stator core 13. A portion of the coils 15 protrudes downward from the lower end surface of the stator core 13. In the embodiment, the coils 15 are wound one by one around each tooth. That is, one coil 15 is wound around each tooth.

[0023] A driving current is supplied to the coils 15 via the connection terminals 10. The coils 15 are connected to each other via crossover wires 11. When the driving current is supplied to the coils 15, a rotating magnetic field is generated between the coils 15 and the rotor 7, causing the rotor to rotate.

[0024] The fixing ring 9 is disposed around the stator core 13. The fixing ring 9 is fixed to the stator core 13.

[0025] The motor case 3 houses the motor 2. The motor case 3 is disposed around the fixing ring 9. The motor case 3 has a case body 4 and a case lid 5.

[0026] A refrigerant flow path 18 is formed on the inner circumferential surface of the case body 4. The refrigerant flow path 18 is formed so as to be recessed radially outward from the inner circumferential surface of the case body 4. The refrigerant flow path 18 is spiral-shaped. The refrigerant flow path 18 is provided so as to circle around the rotation axis AX. Note that the refrigerant flow path 18 may be pulse-shaped.

[0027] The refrigerant flow path 18 is connected to each of the refrigerant supply circuit 16 and the refrigerant discharge circuit 17. The refrigerant is supplied to the refrigerant flow path 18 via the refrigerant supply circuit 16. The refrigerant flows through the refrigerant flow path 18. The refrigerant that has flowed through the refrigerant flow path 18 is discharged from the refrigerant flow path 18 via the refrigerant discharge circuit 17.

[0028] The case lid 5 is disposed so as to close the opening at the upper end of the case body 4. The case body 4 and the case lid 5 are fixed together with bolts 6. The internal space of the motor case 3 is an airtight space.

[0029] Fig. 3 is a schematic view of a portion of the rotor 7 according to the embodiment, as seen from above. Fig. 4 is a schematic view of a portion of the rotor 7 according to the embodiment, as seen from above. Fig. 4 corresponds to an enlarged view of a portion of Fig. 3. Fig. 5 is a schematic view of a portion of the rotor 7 according to the embodiment, as seen from above. Fig. 6 is a schematic view of the rotor 7 according to the embodiment, as seen from above.

[0030] The rotor core 21 has a plurality of magnet holes 24 spaced apart in the circumferential direction, and air gaps 30 provided on both sides of the magnet holes 24 in the circumferential direction with partition walls 50 interposed therebetween.

[0031] The partition wall 50 is a part of the rotor core 21. The partition wall 50 separates the magnet holes 24 from the air gaps 30. The magnet holes 24 and the air gaps 30 are each formed by, for example, drilling the rotor core 21. The magnet holes 24 and the air gaps 30 are not connected to each other.

[0032] A gap 30 is provided on both circumferential sides of each of the multiple magnet holes 24, with a partition wall 50 interposed therebetween. The distance between a magnet hole 24 and the gap 30 located on the forward circumferential side of the magnet hole 24 is equal to the distance between a magnet hole 24 and the gap 30 located on the reverse circumferential side of the magnet hole 24.

[0033] Magnet holes 24 are provided so as to penetrate through the upper end surface and the lower end surface of rotor core 21. Air gaps 30 are provided so as to penetrate through the upper end surface and the lower end surface of rotor core 21.

[0034] In a plane perpendicular to the rotation axis AX, the magnet hole 24 has a rectangular shape that is elongated in the circumferential direction. In a plane perpendicular to the rotation axis AX, the permanent magnet 22 has a rectangular shape that is elongated in the circumferential direction. The radially outward end face and the radially inward end face of the permanent magnet 22 each contact the inner surface of the magnet hole 24. The circumferentially forward end face and the circumferentially reverse end face of the permanent magnet 22 each contact the inner surface of the magnet hole 24. In other words, the permanent magnet 22 is arranged without any gaps in the magnet hole 24. As shown in FIG. 4 , a small gap 25 may exist between the corner of the permanent magnet 22 and the magnet hole 24. A small gap may also exist between the outer periphery of the permanent magnet 22 and the magnet hole 24. The gap 25 may be filled with synthetic resin.

[0035] In the circumferential direction, the dimension of the air gap 30 is smaller than the dimension of the magnet hole 24. In the radial direction, the dimension of the air gap 30 is larger than the dimension of the magnet hole 24. In the radial direction, the outer end of the air gap 30 is positioned radially outward of the outer end of the magnet hole 24.

[0036] 4, the circumferential dimension Wa of the radially inner edge of the gap 30 is smaller than the circumferential dimension Wb of the radially outer edge of the gap 30. The circumferential dimension of the gap 30 increases radially outward. In a plane perpendicular to the rotation axis AX, the shape of the gap 30 is substantially trapezoidal.

[0037] 3 and 4, the second magnet hole 24B is provided adjacent to the first magnet hole 24A on the forward circumferential side. The distance F between the first air gap 30A provided on the forward circumferential side of the first magnet hole 24A and the second air gap 30B provided on the reverse circumferential side of the second magnet hole 24B is greater than the dimension G of the partition wall 50 in the circumferential direction.

[0038] The rotor core 21 has a first recess 41 recessed radially inward from the outer peripheral surface of the rotor core 21, and a second recess 42 recessed radially inward from the outer peripheral surface of the rotor core 21. Each of the first recess 41 and the second recess 42 is a groove-like shape that is long in the axial direction. The first recess 41 is provided across the upper end and the lower end of the rotor core 21. The second recess 42 is provided across the upper end and the lower end of the rotor core 21.

[0039] In the circumferential direction, the first recess 41 is located closer to the first magnet hole 24A than the center of the first gap 30A. As shown in Figure 4, the gap 30A has an edge EL that is adjacent to the magnet hole 24A and extends in the radial direction. At least a portion of the first recess 41 is located on an extension line that extends radially outward from the edge EL.

[0040] In the circumferential direction, the second recess 42 is provided between the first gap 30A and the second gap 30B.

[0041] 5 and 6 , in a plane perpendicular to the rotation axis AX of the rotor 7, the angle formed by a first line connecting the rotation axis AX and the end of the first recess 41 on the reverse circumferential side and a second line connecting the rotation axis AX and the end of the first recess 41 on the forward circumferential side is defined as θi. The angle formed by the first line and a reference axis RL, which is a third line connecting the rotation axis AX and the centers of the first gap 30A and the second gap 30B, is defined as θil. The angle formed by the reference axis RL and the second line is defined as θis. The number of pole pairs of the rotor 7 is defined as p. The reference axis RL is a line passing through the centers of the first gap 30A and the second gap 30B in the circumferential direction. In this case, the first recess 41 satisfies the following condition.

[0042] θi=θil-θis...(1) θis<θil...(2) 24 / p≦θis≦34 / p...(3) 24 / p≦θil≦34 / p...(4)

[0043] 5 and 6 , in a plane perpendicular to the rotation axis AX of the rotor 7, the angle formed by a fourth line connecting the rotation axis AX and the end of the second recess 42 on the reverse circumferential side and a fifth line connecting the rotation axis AX and the end of the second recess 42 on the forward circumferential side is defined as θo. The angle formed by the fourth line and a reference axis RL, which is a third line connecting the rotation axis AX and the centers of the first and second air gaps 30A and 30B, is defined as θol. The angle formed by the third line and the fifth line is defined as θos. The number of pole pairs is defined as p. The reference axis RL is a line passing through the centers of the first and second air gaps 30A and 30B in the circumferential direction. In this case, the second recess 42 satisfies the following condition.

[0044] θo=θol-θos...(5) θos<θol...(6) 0≦θos≦10 / p...(7) 0≦θol≦10 / p...(8)

[0045] 7 is a diagram showing the relationship between cogging torque and torque according to the embodiment, in which the horizontal axis represents the value of [θis / p-θil / p] and the vertical axis represents cogging torque and torque.

[0046] As shown in FIG. 7 , the provision of the first recess 41 reduces cogging torque and increases torque. As indicated by the arrow Ya, a larger value on the horizontal axis indicates that the first recess 41 is positioned closer to the gap 30. Furthermore, the larger the value on the horizontal axis, the smaller the cogging torque and the larger the torque. Line SL indicates the upper limit of the mechanical strength of the rotor 7. If the condition exceeds line SL, the mechanical strength of the rotor 7 falls below the allowable value. Therefore, as indicated by the arrow Yb, it is best to select a value on the horizontal axis that is smaller than line SL. The best value on the horizontal axis is a value close to line SL within a range smaller than line SL. By satisfying the conditions of the above-described equations (1) to (4), cogging torque can be suppressed without reducing torque while suppressing a decrease in rotor strength.

[0047] Fig. 8 is a diagram showing the relationship between cogging torque and torque ripple depending on the angle θo according to the embodiment. Fig. 9 is a diagram showing the relationship between torque and the angle θo according to the embodiment. In Fig. 8, the horizontal axis represents the value of [θos / p-θol / p], and the vertical axis represents torque ripple and cogging torque. In Fig. 9, the horizontal axis represents the value of [θos / p-θol / p], and the vertical axis represents torque.

[0048] As indicated by arrow Yc in FIG. 8 , the smaller the value on the horizontal axis, the more the torque ripple decreases. However, in the range indicated by arrow Yd, the cogging torque increases. By setting the value on the horizontal axis smaller than the range indicated by arrow Yd, both the torque ripple and the cogging torque can be reduced. On the other hand, as indicated by arrow Ye in FIG. 9 , the smaller the value on the horizontal axis, the more the torque decreases. Therefore, by setting the value on the horizontal axis to a value indicated in range Ra, it is possible to maintain torque while reducing both the torque ripple and the cogging torque. In this embodiment, by satisfying the conditions of the above-described equations (5) to (8), it is possible to maintain torque while reducing both the torque ripple and the cogging torque.

[0049] [Effects] As described above, according to the embodiment, it is possible to suppress cogging torque and torque ripple without reducing torque, thereby improving the energy efficiency of the motor 2. Furthermore, according to the embodiment, the partition wall 50 is provided between the magnet holes 24 in which the permanent magnets 22 are arranged and the air gap 30, so that mechanical strength due to centrifugal force can be maintained and a reduction in strength of the rotor 7 can be suppressed. According to the embodiment, it is possible to obtain a flux barrier effect while a reduction in strength of the rotor 7 is suppressed.

[0050] 1...motor device, 2...motor, 3...motor case, 4...case body, 5...case lid, 6...bolt, 7...rotor, 8...stator, 9...fixing ring, 10...connecting terminal, 11...crossover wire, 13...stator core, 14...insulator, 15...coil, 16...refrigerant supply circuit, 17...refrigerant discharge circuit, 18...refrigerant flow path, 21...rotor core, 22...permanent magnet, 23...rotor shaft, 24...magnet hole, 24A...first magnet hole, 24B...second magnet hole, 25...gap, 30...air gap, 30A...first air gap, 30B...second air gap, 41...first recess, 42...second recess, 50...partition wall.

Claims

1. A motor comprising a rotor having a rotor core, the rotor core having a magnet hole and a gap provided on both circumferential sides of the magnet hole via a partition wall.

2. The motor according to claim 1, wherein the rotor core has a plurality of recesses recessed radially inward from its outer circumferential surface.

3. The motor according to claim 1, further comprising a permanent magnet disposed in said magnet hole, wherein a circumferential end face of said permanent magnet contacts an inner surface of said magnet hole.

4. The motor according to claim 1, wherein the gap is provided so as to penetrate from one axial end face of the rotor core to the other axial end face.

5. The motor according to claim 4, wherein the circumferential dimension of the gap increases radially outward.

6. The motor described in claim 2, wherein the magnet holes are provided in a plurality of spaces spaced apart in the circumferential direction, a second magnet hole is provided adjacent to one circumferential side of a first magnet hole, and the distance between a first gap provided on one circumferential side of the first magnet hole and a second gap provided on the other circumferential side of the second magnet hole is greater than the dimension of the partition wall in the circumferential direction.

7. The motor according to claim 6, wherein the recesses include a first recess provided at a position closer to the first magnet hole than the center of the first gap in the circumferential direction.

8. The motor according to claim 7, wherein the first gap is adjacent to the first magnet hole and has an edge extending in a radial direction, and at least a portion of the first recess is provided on an extension line of the edge.

9. The motor according to claim 7, wherein, in a plane perpendicular to the rotation axis of the rotor, an angle formed by a first line connecting the rotation axis and an end of the first recess on the other circumferential side, and a second line connecting the rotation axis and an end of the first recess on one circumferential side is θi, an angle formed by a third line connecting the rotation axis and the center of the first gap and the second gap, and the first line is θil, an angle formed by the third line and the second line is θis, and the number of pole pairs is p, satisfying the following conditions: θi = θil - θis, θis < θil, 24 / p ≤ θis ≤ 34 / p, 24 / p ≤ θil ≤ 34 / p.

10. The motor according to claim 7, wherein the recess includes a second recess provided between the first gap and the second gap in the circumferential direction.

11. The motor according to claim 10, wherein, in a plane perpendicular to the rotation axis of the rotor, an angle formed by a fourth line connecting the rotation axis and the other circumferential end of the second recess, and a fifth line connecting the rotation axis and one circumferential end of the second recess is θo, an angle formed by a third line connecting the rotation axis and the center of the first gap and the second gap, and the fourth line is θol, an angle formed by the third line and the fifth line is θos, and the number of pole pairs is p, satisfying the following conditions: θo=θol-θos, θos<θol, 0≦θos≦10 / p, 0≦θol≦10 / p.

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