Electric motors and motor drive systems

Abstract

To provide suitable electric motors and motor drive systems for aircraft such as electric vertical take-off and landing aircraft. [Solution] The electric motor 16 comprises an annular stator 32 having coils 48, a rotor 34 having a plurality of magnets 58 arranged to surround the outer circumference of the stator 32, an outer cylindrical portion 62 holding the plurality of magnets 58, and an inner cylindrical portion 60 located inside the stator 32, and a heat exchanger 82 that performs heat exchange between a refrigerant for cooling the coils 48 of the stator 32 and outside air, the heat exchanger 82 being positioned between the stator 32 and the inner cylindrical portion 60 of the rotor 34.

Description

Technical Field

[0001] The present disclosure relates to an electric motor and a motor drive system.

Background Art

[0002] U.S. Patent Application Publication No. 2024 / 0116627 discloses that in an Electric Vertical Take-Off and Landing aircraft, a lift propeller generates cooling airflow for cooling a lift motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] There is a demand for a suitable electric motor and a motor drive system in flying objects such as electric vertical take-off and landing aircraft.

[0005] The present disclosure aims to solve the above-mentioned problems.

Means for Solving the Problems

[0006] A first aspect of the present disclosure is an electric motor, comprising: an annular stator having a coil; a rotor having a plurality of magnets arranged to surround an outer periphery of the stator, an outer cylinder portion holding the plurality of magnets, and an inner cylinder portion positioned more inward than the stator; and a heat exchanger that performs heat exchange between a coolant for cooling the coil of the stator and outside air, wherein the heat exchanger is disposed between the stator and the inner cylinder portion of the rotor.

[0007] A second aspect of the present disclosure is a motor drive system comprising an electric motor according to the first aspect, the system further comprising: an inverter that converts DC power supplied from a power source into AC power and supplies it to the coil; a first partial flow path for cooling the inverter with the refrigerant that has flowed through the heat exchanger; and a second partial flow path for cooling the coil of the stator with the refrigerant that has flowed through the first partial flow path. [Effects of the Invention]

[0008] This disclosure provides suitable electric motors and motor drive systems. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of the aircraft. [Figure 2] Figure 2 is a side view of the VTOL rotor and drive unit. [Figure 3] Figure 3 is a perspective view of the drive unit. [Figure 4] Figure 4 is a longitudinal cross-sectional view of the drive unit. [Figure 5] Figure 5 is a cross-sectional view of the drive unit. [Figure 6] Figure 6 is an enlarged view of the area within frame F1 in Figure 5. [Figure 7] Figure 7 is an enlarged view of the area within frame F2 in Figure 5. [Figure 8] Figure 8 is a system configuration diagram of the motor drive system. [Modes for carrying out the invention]

[0010] An electric vertical take-off and landing (eVTOL) aircraft is equipped with a propeller that provides thrust to the airframe and an electric motor that rotates the propeller. The electric motor is cooled by a coolant such as a coolant. In this case, the coolant absorbs heat from the electric motor and dissipates it in a heat exchanger.

[0011] In aircraft such as eVTOL aircraft, miniaturization and weight reduction of various components and systems are desirable in order to ensure flight range. Miniaturization and weight reduction are also desirable in the aircraft's propulsion system. According to the disclosures of this specification, miniaturization and weight reduction of electric motors and motor drive systems installed in aircraft can be achieved.

[0012] [1 Flying object 10] Figure 1 is a schematic diagram of the aircraft 10. The aircraft 10 is an eVTOL aircraft. The aircraft 10 is equipped with eight VTOL rotors 12. The VTOL rotors 12 generate upward thrust relative to the airframe 14. The aircraft 10 is equipped with eight electric motors 16. One electric motor 16 drives one VTOL rotor 12. The aircraft 10 has two cruise rotors 18. The cruise rotors 18 generate forward thrust relative to the airframe 14. The aircraft 10 is equipped with four electric motors 20. Two electric motors 20 drive one cruise rotor 18.

[0013] The electric motor 16 that drives the VTOL rotor 12, together with the inverter 98 (Figure 4), which will be described later, constitutes the drive unit 22.

[0014] The aircraft 10 comprises a pair of booms 26 extending along the front-rear direction. Each boom 26 is connected to a front wing 28 and a rear wing 30. One of the pair of booms 26 is positioned on the right side of the aircraft 10. The other of the pair of booms 26 is positioned on the left side of the aircraft 10. Each boom 26 holds four drive units 22.

[0015] [2 Drive Unit 22] Figure 2 is a side view of the VTOL rotor 12 and the drive unit 22. Figure 3 is a perspective view of the drive unit 22. Figure 4 is a longitudinal sectional view of the drive unit 22. In Figure 4, a flow path through which a cooling liquid such as oil flows is omitted. Figure 5 is a cross-sectional view of the drive unit 22. Figure 5 shows a cut surface along the V-V line shown in Figure 4. Figure 6 is an enlarged view within the frame F1 in Figure 5. Figure 7 is an enlarged view within the frame F2 in Figure 5.

[0016] In the following description, the "radial direction" means the radial direction of a circle centered on the axis A of the drive unit 22 (and the electric motor 16). In addition, the "circumferential direction" means the circumferential direction of a circle centered on the axis A of the drive unit 22 (and the electric motor 16).

[0017] As shown in Figure 4, the drive unit 22 includes an electric motor 16. The electric motor 16 is an outer rotor type multi-phase AC motor (for example, a three-phase AC motor). The electric motor 16 includes a motor holding member 36, an annular stator 32, and a rotor 34. The respective axes A of the drive unit 22, the electric motor 16, the stator 32, and the rotor 34 coincide with one another. The axis A extends along the vertical direction.

[0018] (Motor holding member 36) As shown in Figure 4, the motor holding member 36 includes a mounting portion 38, a stator holding portion 40, a rotor holding portion 42, and a connecting portion 44. Each of the mounting portion 38, the stator holding portion 40, and the rotor holding portion 42 has an annular shape. The mounting portion 38 is mounted to the boom 26. The stator holding portion 40 is connected above the mounting portion 38. The stator holding portion 40 is disposed radially outward of the rotor holding portion 42. The stator 32 is mounted on the outer periphery of the stator holding portion 40. The rotor holding portion 42 is disposed radially inward of the stator holding portion 40. The inner cylindrical portion 60 of the rotor 34 is mounted to the inner periphery of the rotor holding portion 42 via a bearing 68. The connecting portion 44 is disposed between the stator holding portion 40 and the rotor holding portion 42. The connecting portion 44 connects the stator holding portion 40 and the rotor holding portion 42. The stator holding portion 40, the rotor holding portion 42, and the connecting portion 44 function as a heat exchanger 82 described later.

[0019] The motor holding member 36 holds the stator 32 and rotatably holds the rotor 34. Further, the stator holding portion 40, the rotor holding portion 42, and the connecting portion 44 keep the position of the rotor 34 relative to the stator 32 constant.

[0020] (Stator 32) As shown in Figures 5 and 6, the stator 32 has a stator core 46 and coils 48 for each phase. The stator core 46 has a substantially cylindrical shape along axis A. The stator core 46 has a plurality of teeth 50 that project outward in the radial direction. The plurality of teeth 50 are arranged at equal intervals along the circumferential direction. A slot 52 is formed between two adjacent teeth 50. A coil 48 for one of the three phases is wound around each tooth 50. One slot 52 has a coil 48a wound around one of two adjacent teeth 50 and a coil 48b wound around the other of two adjacent teeth 50. In one slot 52, a pipe (second partial flow path) 54 is arranged along axis A between the coil 48a and the coil 48b. Cooling liquid for cooling the coils 48 flows through the pipe 54. The inner circumference of the stator core 46 is attached to the stator holding portion 40 of the motor holding member 36. The stator 32 is held by the motor holding member 36. If the coolant is oil, the coil 48 may be cooled directly by filling the slot 52 with oil. In this case, the piping 54 is not necessary.

[0021] (Rotor 34) As shown in Figure 4, the rotor 34 has a rotor case 56, a rotor core 57, and a plurality of magnets 58. The rotor case 56 is composed of an inner cylinder portion 60, an outer cylinder portion 62, a connecting portion 64, and a VTOL rotor holding portion 66. Each of the inner cylinder portion 60 and the outer cylinder portion 62 has a substantially cylindrical shape along axis A. The inner cylinder portion 60 is positioned radially inward from the outer cylinder portion 62. The outer cylinder portion 62 is positioned radially outward from the inner cylinder portion 60. The connecting portion 64 connects the inner cylinder portion 60 and the outer cylinder portion 62. The VTOL rotor holding portion 66 protrudes upward from the connecting portion 64. As shown in Figure 2, the VTOL rotor 12 is attached to the VTOL rotor holding portion 66. The VTOL rotor holding portion 66 holds the VTOL rotor 12 from below.

[0022] As shown in Figures 5 and 6, a roughly cylindrical rotor core 57 is attached to the inner circumference of the outer cylinder 62. Multiple magnets 58 are attached to the inner circumference of the rotor core 57. In other words, the outer cylinder 62 holds the rotor core 57 and the multiple magnets 58. The multiple magnets 58 are arranged to surround the outer circumference of the stator 32.

[0023] As shown in Figure 4, the inner cylinder portion 60 is inserted into each of the two bearings 68 and the collar 70. For example, the inner ring 68i of each bearing 68 is fitted into the inner cylinder portion 60. The collar 70 is positioned between the two bearings 68. The outer ring 68o of each bearing 68 is attached to the rotor holding portion 42 of the motor holding member 36. The inner cylinder portion 60 is held by the motor holding member 36 via the two bearings 68.

[0024] As shown in Figures 3 and 4, a blower section 72 is formed in the connection section 64. In a plan view (arrow a in Figure 4), the blower section 72 is formed radially outward from the base end 66a of the VTOL rotor holding section 66. The blower section 72 has a plurality of fan blades 74. The plurality of fan blades 74 are arranged along the circumferential direction. A gap 76 is formed between two adjacent fan blades 74, through which outside air can pass. The plurality of fan blades 74 blow air to the heat exchanger 82 located below as the rotor 34 rotates.

[0025] As shown in Figure 4, the connection portion 64 has an annular projection (first projection) 78 that protrudes toward the heat exchanger 82 located below, and an annular projection (second projection) 80 that also protrudes toward the heat exchanger 82. In a plan view (direction a of arrow in Figure 4), the protruding end 78a of the projection 78 is positioned radially inward from the blower portion 72 and radially outward from the rotor holding portion 42. In other words, in a plan view (direction a of arrow in Figure 4), the rotor holding portion 42 is positioned radially inward from the protruding end 78a of the projection 78. In a side view, the protruding end 78a of the projection 78 overlaps with the rotor holding portion 42. On the other hand, in a plan view (direction a of arrow in Figure 4), the protruding end 80a of the projection 80 is positioned radially outward from the blower portion 72 and radially inward from the stator holding portion 40. In other words, in a plan view (arrow a in Figure 4), the stator retaining portion 40 is positioned radially outward from the protruding end 80a of the protruding portion 80. In a side view, the protruding end 80a of the protruding portion 80 overlaps with the stator retaining portion 40.

[0026] The protrusions 78 and 80, the rotor retaining portion 42, and the stator retaining portion 40 function as guides for the outside air blown from the fan blades 74 to the heat exchanger 82. This structure makes it possible to suppress leakage of outside air from the outside air intake passage from the fan blades 74 to the heat exchanger 82.

[0027] (heat exchanger 82) As shown in Figure 4, the electric motor 16 is equipped with an annular (cylindrical) heat exchanger 82. The heat exchanger 82 is also called a radiator. The heat exchanger 82 is integrally formed with the motor holding member 36. The heat exchanger 82 and the motor holding member 36 may be integrally molded, or the components constituting the heat exchanger 82 and the components constituting the motor holding member 36 may be joined by bolts, rivets, etc. As described above, the heat exchanger 82 constitutes the stator holding portion 40, the rotor holding portion 42, and the connecting portion 44 of the motor holding member 36. The heat exchanger 82 is positioned between the stator 32 and the bearing 68 (and inner cylinder portion 60) of the rotor 34. The heat exchanger 82 connects the stator 32 and the bearing 68.

[0028] Thus, the heat exchanger 82 also functions as the stator holder 40, rotor holder 42, and connecting part 44 of the rotor holder 42. With this structure, there is no need to provide the heat exchanger 82 and the connecting part 44 (and the stator holder 40 and rotor holder 42) separately, thus reducing the number of parts in the drive unit 22. In other words, this structure makes the drive unit 22 lighter and more compact.

[0029] As shown in Figure 7, the heat exchanger 82 has an inner annular channel 84, an outer annular channel 86, and a plurality of radiating channels 88. The inner annular channel 84 is an annular channel formed on the inner circumference of the heat exchanger 82. The inner annular channel 84 has a supply port 82a, which is the inlet for the coolant to the heat exchanger 82. The outer annular channel 86 is an annular channel formed on the outer circumference of the heat exchanger 82. The outer annular channel 86 has an outlet port 82b (Figure 5), which is the outlet for the coolant from the heat exchanger 82. The radiating channels 88 are channels that extend radially from the inner annular channel 84 to the outer annular channel 86. The plurality of radiating channels 88 are arranged at equal intervals along the circumferential direction of the heat exchanger 82. Each radiating channel 88 connects the inner annular channel 84 and the outer annular channel 86.

[0030] Between the inner annular channel 84 and the outer annular channel 86, there are multiple heat dissipation fins 90a arranged radially and multiple heat dissipation fins 90b arranged circumferentially. Furthermore, multiple ventilation passages 92 are formed between the inner annular channel 84 and the outer annular channel 86. The ventilation passages 92 pass through the motor holding member 36 along axis A.

[0031] (Wind guide plate 94) As shown in Figure 4, the drive unit 22 is equipped with an air guide plate 94. The air guide plate 94 is located below the heat exchanger 82. The air guide plate 94 is connected to an exhaust port 96 that opens below the drive unit 22. The air guide plate 94 guides outside air that has passed through the air passage 92 of the heat exchanger 82 to the exhaust port 96.

[0032] (Inverter 98) As shown in Figure 4, the drive unit 22 includes an inverter 98. The inverter 98 converts DC power supplied from the power supply 102 (Figure 8) into AC power and supplies it to the coil 48. The inverter 98 is located below the heat exchanger 82. An air guide plate 94 is interposed between the heat exchanger 82 and the inverter 98. In a plan view (arrow a in Figure 4), the inverter 98 is located inside the stator 32 and the stator holder 40, and outside the rotor 34, bearing 68, and rotor holder 42. By placing the inverter 98 in this dead space, the drive unit 22 can be miniaturized.

[0033] (Motor drive system 100) Figure 8 is a system configuration diagram of the motor drive system 100. The motor drive system 100 comprises a power supply 102, an inverter 98, and an electric motor 16. The power supply 102 supplies power to the coil 48 of the electric motor 16 via the inverter 98.

[0034] The motor drive system 100 includes a cooling circuit 104. The cooling circuit 104 circulates a coolant. The cooling circuit 104 has a tank 106, a pump 108, and a plurality of partial flow paths 110, 112, 114, 116, 118, and 120.

[0035] The upstream end 110a of partial flow path 110 is connected to tank 106. The downstream end 110b of partial flow path 110 is connected to the inlet 108a of pump 108. The upstream end 112a of partial flow path 112 is connected to the discharge port 108b of pump 108. The downstream end 112b of partial flow path 112 is connected to the supply port 82a of heat exchanger 82. The upstream end 114a of partial flow path 114 is connected to the outlet 82b of heat exchanger 82. The downstream end 114b of partial flow path 114 is connected to the upstream end 118a of partial flow path 118. The upstream end 116a of partial flow path (first partial flow path) 116 is connected to the upstream part of partial flow path 114. The downstream end 116b of partial flow path 116 is connected to the downstream part of partial flow path 114. The upstream end 118a of the partial channel (second partial channel) 118 is connected to the downstream end 114b of the partial channel 114. The downstream end 118b of the partial channel 118 is connected to the upstream end 120a of the partial channel 120. The upstream end 120a of the partial channel 120 is connected to the downstream end 118b of the partial channel 118. The downstream end 120b of the partial channel 120 is connected to the tank 106.

[0036] The partial flow path 116 is arranged along the circuit board (not shown) of the inverter 98. This allows the inverter 98 to be cooled by the coolant. The partial flow path 118 is arranged along the coil 48. The partial flow path 118 corresponds to the piping 54 shown in Figures 4 and 6. This allows the coil 48 to be cooled by the coolant. Since the control temperature of the coil 48 is higher than the control temperature of the inverter 98, the temperature of the coil 48 will be higher than the temperature of the inverter 98. For this reason, in the cooling circuit 104, the partial flow path 116 is arranged on the upstream side and the partial flow path 118 is arranged on the downstream side.

[0037] [3 Operation of the drive unit 22 and motor drive system 100] The flow of outside air will be explained using Figure 4. The power supply 102 shown in Figure 8 supplies power to the electric motor 16 via the inverter 98. The rotor 34 rotates as the coils 48 of each phase are periodically energized. As the rotor 34 rotates, each fan blade 74 of the blower unit 72 blows outside air to the heat exchanger 82. The outside air passes through the air passage 92 (Figure 7) of the heat exchanger 82, flows along the guide plate 94, and is discharged to the outside of the drive unit 22 from the exhaust port 96.

[0038] The flow of the coolant will be explained using Figure 8. Pump 108 draws coolant from tank 106 via partial flow path 110 and discharges it into partial flow path 112. The coolant flows through partial flow path 112 and into heat exchanger 82. In heat exchanger 82, the coolant flows through the inner annular flow path 84, each radiating flow path 88 and outer annular flow path 86 shown in Figure 7, and is discharged from heat exchanger 82. In heat exchanger 82, the coolant dissipates heat to the outside air passing through the ventilation passage 92 via heat dissipation fins 90a and 90b. The coolant discharged from heat exchanger 82 flows through partial flow paths 114, 116, 118 and 120 and returns to tank 106. In partial flow path 116, the coolant absorbs heat from inverter 98. In partial flow path 118 (piping 54), the coolant absorbs heat from coil 48. In this manner, the coolant absorbs heat from the inverter 98 and coil 48 and dissipates it into the outside air in the heat exchanger 82.

[0039] [4 Note] The following additional information is disclosed regarding the above embodiment.

[0040] (Note 1) The electric motor (16) of the present disclosure comprises an annular stator (32) having coils (48), a rotor (34) having a plurality of magnets (58) arranged to surround the outer circumference of the stator, an outer cylindrical portion (62) holding the plurality of magnets, and an inner cylindrical portion (60) located inside the stator, and a heat exchanger (82) that performs heat exchange between a refrigerant for cooling the coils of the stator and outside air, wherein the heat exchanger is disposed between the stator and the inner cylindrical portion of the rotor.

[0041] With the above configuration, the drive unit equipped with an electric motor can be made lighter and more compact.

[0042] (Note 2) In the electric motor described in Appendix 1, a bearing (68) is provided attached to the outer circumference of the inner cylinder portion of the rotor, and the heat exchanger may connect the stator and the bearing.

[0043] (Note 3) In the electric motor described in Appendix 2, the rotor has a connecting portion (64) that connects the inner cylinder portion and the outer cylinder portion, and a plurality of fan blades (74) are formed on the connecting portion, which are arranged along the circumferential direction of the rotor and blow air to the heat exchanger as the rotor rotates.

[0044] (Note 4) In the electric motor described in Appendix 3, the connection portion has an annular first projection (78) projecting toward the heat exchanger and an annular second projection (80) projecting toward the heat exchanger, the heat exchanger has an annular stator holding portion (40) for holding the stator and an annular rotor holding portion (42) for holding the rotor, the projection end (78a) of the first projection is positioned radially inward from the plurality of fan blades in a plan view, the rotor holding portion is positioned radially inward from the projection end of the first projection in a plan view, the projection end of the first projection overlaps with the rotor holding portion in a side view, the projection end (80a) of the second projection is positioned radially outward from the plurality of fan blades in a plan view, the stator holding portion is positioned radially outward from the projection end of the second projection in a plan view, and the projection end of the second projection may overlap with the stator holding portion in a side view.

[0045] With the above configuration, leakage of outside air from the outside air intake path from the fan blades to the heat exchanger can be suppressed.

[0046] (Note 5) The motor drive system (100) of this disclosure comprises an electric motor as described in any one of appendices 1 to 4, an inverter (98) that converts DC power supplied from a power source (102) into AC power and supplies it to the coil, a first partial flow path (116) for cooling the inverter with the refrigerant that has flowed through the heat exchanger, and a second partial flow path (118) for cooling the coil of the stator with the refrigerant that has flowed through the first partial flow path.

[0047] (Note 6) In the motor drive system described in Appendix 5, the inverter may be positioned inside the stator in a plan view.

[0048] The above configuration makes it possible to miniaturize the drive unit equipped with an electric motor.

[0049] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0050] 16…Electric motor 32…Stator 34...Rotor 40...Stator retainer 42...Rotor holder 48...Coil 58...Magnet 60...Inner cylinder 62...Outer cylinder part 64...Connecting part 68...Bearing 74...Fan blade 78...Protrusion part (first protrusion part) 78a...Protrusion end 80...Protrusion part (second protrusion part) 80a...Protrusion end 82…Heat exchanger 98…Inverter 100…Motor drive system 102…Power supply 116...Partial flow path (first partial flow path) 118...Partial flow path (second partial flow path)

Claims

1. An annular stator having a coil, A rotor having a plurality of magnets arranged to surround the outer circumference of the stator, an outer cylindrical portion that holds the plurality of magnets, and an inner cylindrical portion located inside the stator, A heat exchanger that performs heat exchange between a refrigerant and outside air for cooling the coils of the stator, Equipped with, The heat exchanger is an electric motor disposed between the stator and the inner cylinder portion of the rotor.

2. In the electric motor according to claim 1, The rotor is equipped with a bearing attached to the outer circumference of the inner cylinder portion, The heat exchanger comprises an electric motor connecting the stator and the bearing.

3. In the electric motor according to claim 2, The rotor has a connecting portion that connects the inner cylinder portion and the outer cylinder portion. An electric motor having a plurality of fan blades formed at the connection portion, which are arranged along the circumferential direction of the rotor and blow air onto the heat exchanger as the rotor rotates.

4. In the electric motor described in claim 3, The connecting portion has an annular first projection that protrudes toward the heat exchanger and an annular second projection that protrudes toward the heat exchanger. The heat exchanger has an annular stator holding portion for holding the stator and an annular rotor holding portion for holding the rotor. The protruding end of the first protrusion is positioned radially inward from the plurality of fan blades in a plan view. The rotor holding portion is positioned radially inward from the protruding end of the first protrusion in a plan view. The protruding end of the first protrusion overlaps with the rotor holding portion in a side view. The protruding end of the second protrusion is positioned radially outward from the plurality of fan blades in a plan view. In a plan view, the stator holding portion is positioned radially outward from the protruding end of the second protrusion. The protruding end of the second protrusion overlaps with the stator holding portion in a side view, in an electric motor.

5. A motor drive system comprising an electric motor according to any one of claims 1 to 4, An inverter that converts DC power supplied from a power source into AC power and supplies it to the coil, A first partial flow path for cooling the inverter with the refrigerant that has flowed through the heat exchanger, A second partial flow path for cooling the coil of the stator with the refrigerant that has flowed through the first partial flow path, A motor-driven system equipped with the following features.

6. In the motor drive system according to claim 5, In a plan view, the inverter is positioned inside the stator in a motor drive system.

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