Electric motor

Abstract

To provide an electric motor capable of improving the efficiency of cooling by the air flow generated by a cooling fan.SOLUTION: An electric motor 1 includes a drive shaft 5, a motor 20 that rotates the drive shaft, a heat sink 8 through which the drive shaft passes, and a cooling fan 9 that is fixed to a first end 5a of the drive shaft and faces the heat sink. A plurality of heat dissipation fins 81 are provided on a first surface 8a of the heat sink that faces the cooling fan, and each of the heat dissipation fins has a communicating space 81A that extends circumferentially, and in a cross section perpendicular to the extension direction of the communicating space, the cross-sectional area of the communicating space is approximately constant in the extension direction or increases radially inward.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric motor. [Background technology]

[0002] Electric motors having an inverter unit and a motor unit have been known for some time. In such electric motors, the inverter unit includes an inverter and an inverter case that houses the inverter. The motor unit includes a motor that includes a rotor and a stator that rotate a drive shaft, and a motor frame that houses the motor.

[0003] Because the inverter and motor are heat sources, when the motor is running, heat from the inverter is transferred to the inverter case, causing the inverter case to become hot. Similarly, heat from the motor is transferred to the motor frame, causing the motor frame to become hot. As a result, the motor as a whole can become very hot.

[0004] Therefore, the electric motor is provided with a cooling fan fixed to the drive shaft. The cooling fan rotates with the rotation of the drive shaft and cools the outer surface of the inverter case and the outer surface of the motor frame (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-159692 Summary of the Invention [Problem to be solved by the invention]

[0006] Because the cooling fan is fixed to the drive shaft, when the motor rotation speed decreases, the cooling fan rotation speed also decreases, reducing the airflow. Also, near the center of the cooling fan's rotation shaft (i.e., near the drive shaft), the air flow generated by the rotation of the cooling fan is weaker than near the outer edge of the cooling fan, which can result in insufficient cooling.

[0007] The present invention has been made in view of the above-mentioned problems, and has as its object to provide an electric motor capable of improving the efficiency of cooling by the air flow generated by a cooling fan. [Means for solving the problem]

[0008] (1): An electric motor according to one embodiment of the present invention comprises a drive shaft, a motor for rotating the drive shaft, a heat sink through which the drive shaft passes, and a cooling fan fixed to a first end of the drive shaft and facing the heat sink, wherein a plurality of heat dissipation fins are provided on a first surface of the heat sink facing the cooling fan, and each of the heat dissipation fins has a communicating space extending along the circumferential direction, and in a cross section perpendicular to the extension direction of the communicating space, the cross-sectional area of ​​the communicating space is approximately constant in the extension direction or increases radially inward.

[0009] (2) In the electric motor according to (1), the communication space is a through-hole that penetrates the heat dissipation fin from an upper surface facing the cooling fan to an inner side surface facing radially inward.

[0010] (3) In the electric motor according to (2), the shape of the upper opening of the through hole in the upper surface of the heat dissipation fin is elliptical when viewed in the axial direction.

[0011] (4) In the electric motor according to any one of (1) to (3), the communication space is a groove extending along a radial direction and formed on an upper surface of the heat dissipation fin facing the cooling fan.

[0012] (5) In the electric motor according to (4), the depth of the groove increases toward the inside in the radial direction.

[0013] (6) In the electric motor according to (4) or (5), the groove is U-shaped when viewed from the radial direction.

[0014] (7): In the electric motor according to any one of (1) to (6), the cooling fan has a hub attached to the drive shaft, a disk-shaped main plate provided on the circumferential surface of the hub and extending radially outward, and fan blades provided on the outer surface of the main plate opposite the inner surface facing the heat sink.

[0015] (8): In the electric motor according to (7), the cooling fan includes a second fan blade provided on the inner surface. [Effects of the Invention]

[0016] According to the above aspect of the present invention, it is possible to provide an electric motor that can improve the efficiency of cooling by the air flow generated by the cooling fan. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of an electric motor according to a first embodiment. [Figure 2A] FIG. 2 is a front view of a heat sink of the electric motor according to the first embodiment. [Figure 2B] FIG. 2 is a perspective view of a heat sink of the electric motor according to the first embodiment. [Figure 2C] FIG. 2 is a partially enlarged view of a heat sink of the electric motor according to the first embodiment. [Figure 3A] 1 is a front view of a cooling fan for an electric motor according to a first embodiment, as viewed from the +X direction. [Figure 3B] 2 is a front view of the cooling fan of the electric motor according to the first embodiment, as viewed from the −X direction. FIG. [Figure 3C] FIG. 2 is a perspective view of a cooling fan for the electric motor according to the first embodiment. [Figure 4A] FIG. 10 is a perspective view of a heat sink of an electric motor according to a second embodiment. [Figure 4B]FIG. 10 is a partially enlarged view of a heat sink of an electric motor according to a second embodiment. [Figure 5] FIG. 10 is a partially enlarged view of a heat sink of an electric motor according to a third embodiment. [Figure 6] FIG. 10 is a partially enlarged view of a heat sink of an electric motor according to a fourth embodiment. [Figure 7A] FIG. 10 is a front view of a cooling fan according to a modified example, as viewed from the +X direction. [Figure 7B] FIG. 10 is a front view of a cooling fan according to a modified example, as viewed from the −X direction. [Figure 7C] FIG. 10 is a perspective view of a cooling fan according to a modified example. [Figure 8A] 10A and 10B are diagrams showing modified examples of heat dissipation fins of a heat sink. [Figure 8B] 10A and 10B are diagrams showing other modified examples of the heat dissipation fins of the heat sink. [Figure 9] 10A and 10B are diagrams illustrating the shape of a conventional heat sink. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] (First embodiment) FIG. 1 is a cross-sectional view of an electric motor 1 according to a first embodiment. The electric motor 1 of this embodiment has an integrated structure with an inverter built in. As shown in FIG.

[0020] <Direction definition> In the following description, the direction in which the central axis O of the drive shaft 5 extends is referred to as the axial direction, the direction perpendicular to the central axis O is referred to as the radial direction, and the direction going around the central axis O is referred to as the circumferential direction. In the axial direction, the direction from the motor unit 2 to the inverter unit 3 is referred to as the +X direction, and the direction from the inverter unit 3 to the motor unit 2 is referred to as the -X direction.

[0021] The motor section 2 includes a motor 20 having a rotor 21 fixed to a drive shaft 5 and a stator 22 that surrounds the rotor 21 to form a rotating magnetic field, and a motor frame 10 that houses the rotor 21 and the stator 22. The stator 22 includes a stator core 22a and a coil 22b wound around the stator core 22a. The drive shaft 5 rotates together with the rotor 21 due to the rotating magnetic field generated by the stator 22. The drive shaft 5 has a first end 5a on the +X direction side and a second end 5b on the −X direction side. The motor 20 is, for example, a permanent magnet motor using a permanent magnet in the rotor, an induction motor, an SR motor, or the like.

[0022] The inverter unit 3 has an inverter 31 that controls the operation (rotational speed) of the motor 20. The inverter 31 is provided with an inverter board 32 on which a plurality of heat generating elements including elements such as switching elements and capacitors are mounted. The inverter 31 is housed in a motor frame 10. The motor unit 2 and the inverter unit 3 are separated by a partition wall 11 through which the drive shaft 5 passes. The present invention is not limited to the example in which the motor unit 2 and the inverter unit 3 are housed within the motor frame 10, and the frame housing the motor unit 2 and the frame housing the inverter unit 3 may be separate bodies.

[0023] The motor frame 10 has a main body 10a formed in a cylindrical shape coaxial with the central axis O of the drive shaft 5, and a plurality of peripheral heat dissipation fins 10b extending outward from the outer circumferential surface of the main body 10a. The plurality of peripheral heat dissipation fins 10b are formed integrally with the motor frame 10 and extend linearly along the axial direction. The motor frame 10 accommodates the motor unit 2, the inverter unit 3, and a partition wall 11. Within the motor frame 10, the motor unit 2 and the inverter unit 3 are arranged in series in the axial direction of the drive shaft 5, so that the electric motor 1 has a compact structure.

[0024] A heat sink 8 is provided at the end of the motor frame 10 on the +X side, with the open end on the +X side closed and a through hole 8h through which the drive shaft 5 passes. As shown in FIG. 2A , a first surface 8a on the +X side of the heat sink 8 is formed with a plurality of heat dissipation fins 81 extending upright from the first surface 8a. The heat dissipation fins 81 are arranged at intervals in the circumferential direction and extend radially. As will be described in detail later, each heat dissipation fin 81 has a communication space 81A, which is a space through which air can move. In this embodiment, the communication space 81A is formed as a through hole 81h that passes through the heat dissipation fin 81. A recess 8b1 is formed in the second surface 8b on the -X side of the heat sink 8. An inverter board 32 is provided in the recess 8b1.

[0025] A cooling fan 9 is fixed to the +X side end of the drive shaft 5 (i.e., the anti-load side of the drive shaft 5). The cooling fan 9 is provided on the +X side of the heat sink 8, and is arranged opposite the heat sink 8 in the axial direction.

[0026] 3A to 3C, cooling fan 9 has a hub 91, a main plate 92, and fan blades 93. Cooling fan 9 has a through-hole 9a through which drive shaft 5 passes. The hub 91 is provided at the center of the cooling fan 9, and is attached to the first end 5a of the drive shaft 5. The hub 91 is formed in a cylindrical shape concentric with the central axis O of the drive shaft 5.

[0027] The main plate 92 is a generally circular plate provided on the circumferential surface of the hub 91 and extending radially outward. In a cross-sectional view along the central axis O, the main plate 92 of this embodiment is inclined in the -X direction as it extends radially outward, and therefore the circular plate of the main plate 92 is formed into a generally conical shape. Note that the main plate 92 does not have to be formed into a conical shape. The main plate 92 has an outer surface 92a facing the +X direction and an inner surface 92b facing the −X direction and facing the heat sink 8.

[0028] The fan blades 93 are flat plates disposed radially on the outer surface 92a. The multiple fan blades 93 are disposed at intervals in the circumferential direction. The fan blades 93 have the shape of a centrifugal fan blade. The fan blades 93 may also have a blade shape that curves back from the direction of rotation as they extend radially outward. As shown in FIG. 1, the cooling fan 9 is covered with a fan cover 12.

[0029] The fan cover 12 is a member for sending cooling air toward the inverter unit 3 and the motor unit 2 while preventing the user's fingers from coming into contact with the cooling fan. The fan cover 12 is disposed to cover the cooling fan 9 and heat sink 8 and is fixed to a fixing portion 82 of the heat sink 8 (see FIGS. 1 and 2A). The fan cover 12 has an intake port 12a that faces the cooling fan 9 in the axial direction. As indicated by arrow F1 in FIG. 1, air drawn in through the intake port 12a is discharged from an outlet port 12b that is provided between the fan cover 12 and the heat sink 8 and that discharges the air along the circumferential surface of the motor frame 10. The air sent from the outlet port 12b of the fan cover 12 along the circumferential surface of the motor frame 10 flows along the peripheral heat dissipation fins 10b that are provided on the circumferential surface of the motor frame 10, thereby cooling the inverter unit 3 and the motor unit 2.

[0030] On the −X side of the motor frame 10, a load side bracket 13 is provided which closes the open end on the −X side and through which the drive shaft 5 passes. The load side bracket 13 and the partition wall 11 face each other with the motor 20 sandwiched between them in the axial direction. The drive shaft 5 is rotatably supported by a load side bearing 14 supported by a bearing support portion 13b of the load side bracket 13. The drive shaft 5 is also rotatably supported by a non-load side bearing 15 supported by a bearing support portion 11b of the partition wall 11. The partition wall 11 can also be said to be a non-load side bracket. A load side V ring 16 that seals between the drive shaft 5 and the load side bracket 13 is provided on the −X side of the load side bracket 13 . On the +X side of the heat sink 8, a counter-load side V ring 17 that seals the gap between the drive shaft 5 and the heat sink 8 is provided.

[0031] The motor 20 and the inverter 31 including the inverter board 32 are heat sources. Therefore, in consideration of the heat dissipation properties of these heat source components, it is preferable to use aluminum or iron, which have high thermal conductivity, as the material for the motor frame 10 and the heat sink 8, etc.

[0032] In an electric motor 1 in which the inverter section 3 is provided axially of the motor section 2 and the inverter 31 is integrated within the motor frame 10, both the motor section 2 and the inverter section 3 are heat sources, making the electric motor 1 prone to high temperatures. Furthermore, the temperatures of the motor 20 and the inverter 31 can cause components within the electric motor 1 to burn out, shorten their lifespan, or reduce their operating efficiency. Here, since the cooling fan 9 is integrated with the drive shaft 5, when the rotation speed of the motor 20 decreases, the rotation speed of the cooling fan 9 also decreases, and the airflow decreases. As a result, the cooling effect of the cooling fan 9 on the electric motor 1 may decrease. Furthermore, since the cooling fan 9 is a centrifugal fan that rotates around the central axis O, it is difficult for air to flow into the central portion 8c of the heat sink 8 (see Figure 2A), causing air to stagnate in the central portion 8c, and the cooling of the central portion 8c may not be sufficient compared to the outer edge portion. Therefore, in this embodiment, a communication space 81A is formed in the heat dissipation fins 81 of the heat sink 8, which are exposed to the wind generated by the rotation of the cooling fan 9, to enhance the heat dissipation effect. Below, the shape of the heat sink 8 and the action of the heat sink 8 when cooling a heat-generating body will be described.

[0033] <Heat sink 8> As shown in Figures 2A to 2C, the heat sink 8 includes a disk-shaped base portion 80 having a through hole 8h penetrating in the axial direction, a plurality of heat dissipation fins 81 extending upright from the base portion 80 in the +X direction, and a fixing portion 82 provided on the outer edge of the base portion 80. The base portion 80 is disk-shaped when viewed in the axial direction. The base portion 80 is provided with, in this order from the inside, a main surface portion 80a, an inclined portion 80b whose radially outer side is inclined toward the −X side, an outer peripheral surface portion 80c facing radially outward, and a rim portion 80d facing the +X direction (see FIG. 2B). A recess 8b1 is formed on the second surface 8b of the base portion 80 facing the -X side, in which the inverter board 32 and the like are provided (see FIG. 1). Therefore, the thickness of the base portion 80 in the axial direction is approximately uniform. This allows the thermal resistance of the heat sink 8 to be reduced.

[0034] A plurality of fixing portions 82 are provided at equal intervals in the circumferential direction on the outer edge of the heat sink 8. In this embodiment, the number of fixing portions 82 is three, but the number of fixing portions 82 may be one or more. The fixing portions 82 protrude radially outward beyond the rim portion 80d. The fixing portion 82 has a through-hole 82a that penetrates in the axial direction and a fan cover fixing hole 82b that extends radially inward from the outer circumferential surface of the fixing portion 82. The heat sink 8 is fixed to the motor frame 10 by a screw or the like that passes through the through-hole 82a. The fan cover 12 is fixed to the heat sink 8 by fastening a screw or the like that passes through a through-hole (not shown) of the fan cover 12 to the fan cover fixing hole 82b. The diameter of the opening of the fan cover 12 facing the -X direction is larger than the outer diameter of the main body 10a of the motor frame 10, and the diameter of the base 80 of the heat sink 8 is equal to or smaller than the diameter of the main body 10a of the motor frame 10. Therefore, a gap is provided between the base 80 and the fan cover 12. This gap serves as an outlet 12b (see FIG. 1) for the air generated by the cooling fan 9. The air discharged from the outlet 12b flows between the outer circumferential heat dissipation fins 10b of the motor frame 10 and proceeds in the -X direction (see arrow F1 in FIG. 1).

[0035] <Heat dissipation fins 81 of heat sink 8> The plurality of heat dissipation fins 81 are erected in the +X direction from the base portion 80. The heat dissipation fins 81 extend to a height that does not allow them to come into contact with the cooling fan 9. Each heat dissipation fin 81 extends in the radial direction. As shown in Fig. 2A, the multiple heat dissipation fins 81 are arranged at equal intervals in the circumferential direction when viewed from the axial direction. The heat dissipation fins 81 are formed on the first surface 8a of the heat sink 8, except for a central portion 8c of the base portion 80 near a through-hole 8h through which the drive shaft 5 passes, and the outer edge portion of the rim portion 80d.

[0036] Each heat dissipation fin 81 has a communication space 81A formed therein, which is a space through which air can move within the heat dissipation fin 81. The communication space 81A is a space extending along the radial direction of the heat dissipation fin 81. Hereinafter, the direction in which the communication space 81A extends will be referred to as the extension direction H (see FIG. 2C), and the cross-sectional area of ​​the communication space 81A in a cross section perpendicular to the extension direction H will be referred to as the cross-sectional area A. In this embodiment, each heat dissipation fin 81 has a through-hole 81h that penetrates an upper surface 81u facing the +X direction and an inner side surface 81i facing radially inward, and serves as a communication space 81A. The through-hole 81h extends in a direction that slopes toward the +X side as it extends radially outward. Hereinafter, the extending direction of the through-hole 81h will be referred to as the extension direction H1, and the cross-sectional area A of the through-hole 81h will be referred to as the cross-sectional area A1.

[0037] When viewed from the axial direction, the shape of the top surface opening 81u1 formed in the top surface 81u by the through hole 81h is an ellipse with its minor axis in the circumferential direction and its major axis in the radial direction. When viewed from the radial direction, the shape of the inside opening 81i1 opening in the inside side surface 81i may be substantially circular or may be an ellipse with its minor axis in the circumferential direction and its major axis in the axial direction. When viewed in the axial direction, the top surface opening 81u1 is provided radially outward of the cooling fan 9, and the inner opening 81i1 is provided at a position overlapping with the cooling fan 9. In Fig. 2A, for the sake of explanation, the position of the cooling fan 9 is indicated by a dotted line.

[0038] <Cooling of heat generating elements by heat sink 8> Next, the operation of the heat sink 8 having the above configuration will be described. 1, with the cooling fan 9 configured as described above, when the drive shaft 5 rotates, air is drawn in the axial direction through the inlet 12a of the fan cover 12. The drawn air is discharged radially outward along the outer surface 92a of the main plate 92 due to centrifugal force exerted by the fan blades 93, as shown by the arrow F1.

[0039] Within the space covered by the fan cover 12, air from the cooling fan 9 moves in the -X direction along the arrow F1. Part of the air hits the heat sink 8, which has multiple heat dissipation fins 81, and cools the inverter unit 3. The heat dissipation fins 81 ensure a large surface area in the heat sink 8, allowing it to efficiently cool the heat from the inverter unit 3 and other components. The air further moves in the −X direction, and the air discharged from the outlet 12 b of the fan cover 12 flows along the outer circumferential heat dissipation fins 10 b of the motor frame 10 to cool the inverter section 3 and the motor section 2 .

[0040] At this time, part of the air flowing toward the heat sink 8 passes through the through holes 81h, which are the communication spaces 81A of the heat dissipation fins 81, and is guided toward the vicinity of the central portion 8c on the radially inner side (see arrow F2 in FIG. 1). The air guided toward the vicinity of the central portion 8c moves radially outward from the space between the heat sink 8 and the cooling fan 9. This allows the air from the cooling fan 9 to move efficiently toward the central portion 8c of the heat sink 8, improving the cooling effect of the inverter unit 3. Furthermore, the top surface opening 81u1, which serves as an air inlet to the through hole 81h, has an elliptical shape when viewed from the axial direction, ensuring a wide area for the opening serving as the air inlet. Furthermore, at the location where the top surface opening 81u1 is formed, the cross-sectional area A1 of the through hole 81h increases radially inward, while radially inward from the location where the top surface opening 81u1 is formed, the cross-sectional area A1 of the through hole 81h is substantially constant in the extension direction H1. This allows the cooling air from the cooling fan 9 to be more efficiently guided to the through hole 81h.

[0041] 9, the space between two circumferentially adjacent heat dissipation fins 801 can also be a flow path for the air generated by the cooling fan 9. However, the distance W100 between two adjacent heat dissipation fins 801 on the radially inner side is smaller than the distance W200 between two adjacent heat dissipation fins 801 on the radially outer side. In other words, the space between two adjacent heat dissipation fins 801 narrows radially inward, and it is thought that air may have difficulty flowing radially inward.

[0042] In contrast, in this embodiment, a communication space 81A that extends radially and is a space through which air from the cooling fan 9 can move is provided in each heat dissipation fin 81. The air that moves through this communication space 81A can improve cooling efficiency. Furthermore, the cross-sectional area A of the communication space 81A is substantially constant in the extension direction H or increases radially inward, thereby enabling the air generated by the cooling fan 9 to flow efficiently without impeding the flow of air that has flowed into the communication space 81A.

[0043] The electric motor 1 having the above configuration comprises a drive shaft 5, a motor 20 for rotating the drive shaft 5, a heat sink 8 through which the drive shaft 5 passes, and a cooling fan 9 fixed to the first end 5a of the drive shaft 5 and facing the heat sink 8, and a plurality of heat dissipation fins 81 are provided on the first surface 8a of the heat sink 8 facing the cooling fan 9, and each of the heat dissipation fins 81 has a communicating space 81A extending along the circumferential direction, and in a cross section perpendicular to the extension direction H of the communicating space 81A, the cross-sectional area A of the communicating space 81A is approximately constant in the extension direction H or increases radially inward. According to this configuration, the communication space 81A provided in the heat dissipation fin 81 can improve the efficiency of cooling the inverter section 3 and the motor section 2 using the heat sink 8 by the air flow generated by the cooling fan 9.

[0044] The communication space 81A is a through-hole 81h that penetrates the heat dissipation fin 81 between an upper surface 81u facing the cooling fan 9 and an inner side surface 81i facing radially inward. This makes it possible to provide a flow path for air flowing radially inward within the heat dissipation fins 81. Therefore, it is possible to efficiently cool the electric motor 1 without providing a new flow path for air flowing toward the center portion 8c of the heat sink 8 in the drive shaft 5 or the cooling fan 9. In addition, the electric motor 1 can be made more compact.

[0045] Moreover, when viewed from the axial direction, the shape of the upper surface opening 81u1 of the through-hole 81h in the upper surface 81u of the heat dissipation fin 81 is elliptical. This makes it possible to ensure a large area for the opening that serves as the air inlet to the through-hole 81h.

[0046] The cooling fan 9 also has a hub 91 attached to the drive shaft 5, a disk-shaped main plate 92 provided on the circumferential surface of the hub 91 and extending radially outward, and fan blades 93 provided on the outer surface 92a of the main plate 92 opposite the inner surface 92b facing the heat sink 8. As a result, the air taken in through the suction port 12a can be discharged radially outward along the outer surface 92a of the main plate 92 as indicated by arrow F1 in FIG. 1 by the centrifugal force exerted by the fan blades 93.

[0047] (Second embodiment) Next, a second embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0048] 4A and 4B show the heat sink 8 of the electric motor 1 according to the second embodiment. This embodiment differs from the first embodiment in that the heat dissipation fin 81 has grooves 81g formed on the upper surface 81u thereof as communication spaces 81A, the grooves 81g extending along the radial direction.

[0049] The grooves 81g are recesses recessed in the −X direction from the upper surface 81u, and are U-shaped when viewed from the radial direction. In each heat dissipation fin 81, the depth (axial dimension) of the grooves 81g is constant. In the second embodiment, the extension direction H2 of the groove 81g is the same as the radial direction, and the cross-sectional area A2 of the groove 81g is constant over the entire length in the extension direction H2.

[0050] In the electric motor 1 having the above-described configuration, the communication space 81A is a groove 81g formed on the upper surface 81u of the heat dissipation fin 81 facing the cooling fan 9 and extending along the radial direction. By providing the grooves 81g, a larger surface area can be secured, thereby improving the cooling efficiency compared to a heat sink using heat dissipation fins without grooves 81g. Also, the air that hits the heat sink 8 can move within the grooves 81g. Therefore, the inverter section 3 can be cooled more efficiently by the air flow moving within the grooves 81g.

[0051] Moreover, the groove 81g is U-shaped when viewed from the radial direction. This makes it possible to prevent turbulence in the air within the grooves 81g, and also makes it easier to form the grooves 81g in the heat dissipation fins 81.

[0052] (Third embodiment) Next, a third embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0053] FIG. 5 shows a heat sink 8 of an electric motor 1 according to a third embodiment. In this embodiment, grooves 81r extending along the radial direction are formed on the upper surface 81u of the heat dissipation fin 81. Therefore, the extending direction H3 of the grooves 81r is the same as the radial direction. The groove 81r differs from the second embodiment in that the depth of the groove increases toward the radially inner side, and therefore the cross-sectional area A3 increases toward the radially inner side.

[0054] Alternatively, the grooves 81r may not be formed on the outer edge of the heat dissipation fin 81, but may be formed so that the depth of the grooves 81r increases radially inward. Also, on the inner side surface 81i, the bottoms 81ri of the grooves 81g may be positioned at the same axial position as the main surface 80a of the base portion 80.

[0055] In the above configuration, the depth of the groove 81r increases toward the inside in the radial direction. In this way, the depth of the grooves 81r gradually increases, allowing air to move smoothly toward the radially inward direction. Furthermore, the grooves 81g are formed deeper on the radially inner side, which enhances the effect of guiding air toward the radially inward direction. Furthermore, the provision of the grooves 81r ensures a larger surface area, further improving cooling efficiency.

[0056] (Fourth embodiment) Next, a fourth embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiments will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0057] FIG. 6 shows a heat sink 8 of an electric motor 1 according to a fourth embodiment. In this embodiment, both the through holes 81h described in the first embodiment and the grooves 81g described in the second embodiment are provided in the heat dissipation fins 81. The total cross-sectional area of ​​the communication space 81A is the sum of the cross-sectional area A1 of the through holes 81h and the cross-sectional area A2 of the grooves 81g. More specifically, in the present embodiment, when the cross-sectional area of the first region R1 in which only the radially outer groove 81g is formed is Ar1, the cross-sectional area of the second region R2 in which the upper surface opening 81u1 is formed on the radially inner side of the first region R1 is Ar2, and the cross-sectional area of the third region R3 in which both the through hole 81h and the groove 81g are formed on the radially inner side of the second region R2 is Ar3, then Ar1 < Ar2 < Ar3. Here, the cross-sectional area Ar1 of the first region R1 is substantially constant in the extending direction, the cross-sectional area Ar2 of the second region R2 increases as it goes radially inward in the extending direction, and the cross-sectional area Ar3 of the third region R3 is substantially constant in the extending direction. Thus, the total cross-sectional area A of the communication space 81A is substantially constant in the extending direction H or increases as it goes radially inward.

[0058] According to the electric motor 1 having the above configuration, it is possible to more efficiently cool the electric motor 1 by both the cooling effect of the through hole 81h and the cooling effect of the groove 81g.

[0059] Note that the technical scope of the present invention is not limited to the embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0060] For example, as shown in FIGS. 7A to 7C, a second fan blade 94 (back blade) may be provided on the inner surface 92b of the main board 92 facing the -X direction. The second fan blade 94 has the shape of a fan blade of a centrifugal fan. A plurality of second fan blades 94 are provided on the inner surface 92b of the main board 92 at intervals in the circumferential direction. These plurality of second fan blades 94 are arranged at a distance radially from the circumferential surface of the hub 91 and extend radially about the central axis O. In FIGS. 7A to 7C, the circumferential phase of the second fan blade 94 may be the same as that of the fan blade 93 on the outer surface 92a side described above, but may be different from each other. Also, the number of the second fan blades 94 does not have to be the same as that of the fan blade 93 on the outer surface 92a side described above.

[0061] A conical space surrounded by the inner surface 92b of the main plate 92 is formed on the inner surface 92b side of the main plate 92. Therefore, the axial dimension W94 of the second fan blades 94 gradually increases toward the inside in the radial direction. In addition, the second fan blades 94 rotate in a position where they axially overlap at least a portion of the heat-generating elements of the inverter 31. Therefore, an air flow is formed by the second fan blades 94 on the −X side of the main board 92, thereby improving heat dissipation.

[0062] Furthermore, although the axial height of the heat dissipation fins 81 is constant in the first to fourth embodiments, the height of the heat dissipation fins 81 may decrease radially inward. For example, as shown in FIG. 8A , when one heat dissipation fin 81 is viewed from the circumferential direction, an arc-shaped cutout C may be provided on the radially inner portion. By providing the cutout C, the axial height W1 of the heat dissipation fin 81 on the radially inner side becomes smaller than the axial height W2 of the radially outer side. Note that, as shown in FIG. 8A , a groove 81g may be formed along the radial direction on the upper surface 81u, including the portion where the cutout C is formed. Furthermore, although not shown, a through-hole 81h may be formed penetrating the -X side of the cutout C.

[0063] 8B, the axial height of the heat dissipation fin 81 may gradually decrease toward the radially inner side. In this case, too, the axial height W1 of the heat dissipation fin 81 at the radially inner side is smaller than the axial height W2 of the heat dissipation fin 81 at the radially outer side. Also, as shown in FIG. 8B, through holes 81h may be formed. Furthermore, although not shown, grooves 81g may be formed in the upper surface 81u. In this way, the axial height of the heat dissipation fins 81 is lower on the radially inner side, which makes it easier for air to move to the central portion 8c of the heat sink 8.

[0064] In order to increase the surface area of ​​the heat dissipating fins 81, horizontal holes or rectangular cutouts may be provided through each heat dissipating fin 81 in the circumferential direction.

[0065] In addition, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and the above-described embodiments and variations may be combined as appropriate, without departing from the spirit of the present invention. [Explanation of symbols]

[0066] 1...electric motor, 5...drive shaft, 5a...first end, 5b...second end, 8...heat sink, 8a...first surface, 8b...second surface, 9...cooling fan, 9a...through hole, 10...motor frame, 10a...main body, 10b...peripheral heat dissipation fin, 20...motor, 31...inverter, 81...heat dissipation fin, 81A...communicating space, 81g, 81r...groove, 81h...through hole, 81i...inner side, 81i1...inner opening, 81u...top surface, 81u1...top opening, 91...hub, 92...main plate, 92a...outer surface, 92b...inner surface, 93...fan blade, 94...second fan blade, A, A1, A2, A3, Ar1, Ar2, Ar3...cross-sectional area, H, H1, H2, H3...extension direction, O...central axis

Claims

1. A drive shaft; a motor that rotates the drive shaft; a heat sink through which the drive shaft passes; a cooling fan fixed to a first end of the drive shaft and facing the heat sink, a plurality of heat dissipation fins are provided on a first surface of the heat sink facing the cooling fan; An electric motor in which each of the heat dissipation fins has a communicating space formed therein that extends circumferentially, and in a cross section perpendicular to the extension direction of the communicating space, the cross-sectional area of ​​the communicating space is approximately constant in the extension direction or increases radially inward.

2. The electric motor according to claim 1 , wherein the communication space is a through-hole that penetrates the heat dissipation fin from an upper surface facing the cooling fan to an inner side surface facing radially inward.

3. 3. The electric motor according to claim 2, wherein the shape of the upper opening of each of the through holes in the upper surface of each of the heat dissipating fins is elliptical when viewed in the axial direction.

4. The electric motor according to claim 1 , wherein the communication space is a groove extending along a radial direction and formed on an upper surface of the heat dissipation fin facing the cooling fan.

5. 5. The electric motor according to claim 4, wherein the depth of the groove increases toward the inside in the radial direction.

6. 5. The electric motor according to claim 4, wherein said groove is U-shaped when viewed radially.

7. 4. The electric motor according to claim 1, wherein the cooling fan comprises a hub attached to the drive shaft, a disk-shaped main plate provided on the circumferential surface of the hub and extending radially outward, and fan blades provided on an outer surface of the main plate opposite an inner surface facing the heat sink.

8. 8. The electric motor of claim 7, wherein the cooling fan includes a second fan blade disposed on the inner surface.

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