Electric motor cooling structure

Abstract

This invention provides a cooling structure for an electric motor that can cool the electric motor more uniformly, thereby improving its cooling performance (cooling efficiency). [Solution] The cooling structure 1 for the electric motor comprises a rotor core 51 formed by stacking multiple electromagnetic steel sheets 511 and a stator core 31 formed by stacking multiple electromagnetic steel sheets 311. Each of the multiple electromagnetic steel sheets 511 constituting the rotor core 51 has multiple grooves 512 formed substantially radially on one surface through which oil or the like flows, and each of the multiple electromagnetic steel sheets 311 constituting the stator core 31 has multiple grooves 312 formed substantially radially on one surface through which oil or the like flows.

Description

Technical Field

[0001] The present invention relates to a cooling structure for an electric motor.

Background Art

[0002] In recent years, hybrid electric vehicles (HEVs) that can effectively improve the fuel consumption rate (fuel efficiency) of vehicles by using an engine and an electric motor in combination have been widely put into practical use. In addition, battery electric vehicles (BEVs) that use only an electric motor as a power source and do not emit exhaust gas have also been put into practical use.

[0003] In such hybrid electric vehicles and battery electric vehicles, for example, a small and highly efficient permanent magnet synchronous motor (PM synchronous motor) is preferably used. A permanent magnet synchronous motor is a rotating field type electric motor (electric motor) in which a permanent magnet is built into a rotor and armature windings (stator windings) are provided in a stator.

[0004] By the way, for example, in order to increase the output of an electric motor, an improvement in cooling performance is required to cope with an increase in the amount of heat generated due to an increase in output. Here, for example, Patent Document 1 discloses a cooling structure for a rotor of a rotating electric machine that can efficiently cool the central region in the axial direction of a rotor core and make the cooling performance for the rotor core uniform in the axial direction.

[0005] More specifically, this cooling structure for the rotor of a rotating electric machine includes a rotor core formed by laminating a plurality of magnetic plates in the axial direction of the rotating electric machine, and refrigerant flow path holes for flowing a coolant in the axial direction of the rotating electric machine are formed. The coolant flowing out from the shaft is supplied to the central region in the axial direction of the rotor core through the inner diameter side of the refrigerant flow path holes, and is configured to flow into the refrigerant flow path holes in the central region and flow to both sides in the axial direction of the rotor core.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2013-183481 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] According to the cooling structure for a rotor of a rotating electric machine described in Patent Document 1 above, the axial central region of the rotor core can be efficiently cooled. However, with this cooling structure, it is difficult to cool the entire rotor uniformly, which may result in low cooling performance (cooling efficiency).

[0008] The present invention was made to solve the above-mentioned problems, and aims to provide a cooling structure for an electric motor that can cool the electric motor more uniformly, thereby improving the cooling performance (cooling efficiency). [Means for solving the problem]

[0009] A cooling structure for an electric motor according to one aspect of the present invention comprises a rotor core formed by laminating a plurality of electromagnetic steel sheets and a stator core formed by laminating a plurality of electromagnetic steel sheets, characterized in that a plurality of grooves through which a cooling medium flows are formed substantially radially in each of the plurality of electromagnetic steel sheets constituting the rotor core and / or the plurality of electromagnetic steel sheets constituting the stator core.

[0010] According to one aspect of the present invention, a cooling structure for an electric motor is formed by stacking multiple electromagnetic steel sheets, each having a plurality of grooves arranged substantially radially through which a cooling medium flows, to form a rotor core and / or stator core. Therefore, the area over which the cooling medium flows (contact area), i.e., the cooling area of ​​the rotor core and / or stator core, can be increased. Thus, the rotor core and / or stator core can be cooled more uniformly and more efficiently. [Effects of the Invention]

[0011] According to the present invention, the electric motor can be cooled more uniformly, thereby improving the cooling performance (cooling efficiency). [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view (a cross-sectional view along the radial direction of the rotor) showing the cooling structure of an electric motor according to the embodiment. [Figure 2] This is a cross-sectional view (a cross-sectional view along the axial direction of the rotor) showing the cooling structure of the electric motor according to the embodiment. [Figure 3] This is a cross-sectional view (along the line III-III in Figure 1) showing the cooling structure of the electric motor according to the embodiment. [Figure 4] This is a cross-sectional view (a cross-sectional view along the radial direction of the stator) showing the cooling structure of an electric motor according to the embodiment. [Figure 5] This is a cross-sectional view (a cross-sectional view along the axial direction of the stator) showing the cooling structure of an electric motor according to the embodiment. [Modes for carrying out the invention]

[0013] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Unless otherwise necessary, the same reference numerals will be used for the same or corresponding parts in the drawings. Furthermore, in each drawing, the same reference numerals will be used for the same elements, and redundant descriptions will be omitted.

[0014] First, the configuration of the cooling structure 1 of the electric motor according to this embodiment will be explained using Figures 1 to 5 together. Figure 1 is a cross-sectional view of the rotor 50 constituting the electric motor 10 along the radial direction. Figure 2 is a cross-sectional view of the rotor 50 along the axial direction. Figure 3 is a cross-sectional view along the line III-III in Figure 1. Figure 4 is a cross-sectional view of the stator 30 constituting the electric motor 10 along the radial direction. Figure 5 is a cross-sectional view of the stator 30 along the axial direction.

[0015] The electric motor 10 to which the cooling structure 1 of the electric motor is applied mainly includes a stator (stator) 30 composed of a stator core 31 having an annular cross-section and a plurality of coils 34 wound around the stator core 31, and a rotor (rotor) 50 having a built-in permanent magnet 53 and rotatably disposed inside the stator 30. In this embodiment, an IPM (Interior Permanent Magnet) motor will be described as an example of the electric motor 10.

[0016] The stator 30 is mainly composed of an annular (cylindrical) stator core 31 having a plurality of teeth 33 and stator windings (coils) 34 wound around each of the teeth 33.

[0017] The stator core 31 is formed in an annular (cylindrical) shape, for example, by arranging a plurality of stator segments (split cores) in the circumferential direction of the stator 30. Each stator segment includes an arc-shaped yoke 32 extending in the circumferential direction of the stator core 31 and a plurality of teeth 33 protruding inward in the radial direction of the stator core 31. Each stator segment is formed by laminating, for example, a directional electromagnetic steel sheet 311 such as a silicon steel sheet.

[0018] With this configuration, a plurality of teeth 33 extending radially inward are arranged at predetermined intervals along the circumferential direction on the stator core 31. The teeth 33 are formed so as to have a substantially rectangular (or circular) cross-sectional shape when cut by a plane orthogonal to the radial direction of the stator core 31 (the axis of the teeth 33).

[0019] On the side surface of the teeth 33, stator windings (coils) 34 composed of windings in which a highly conductive wire such as copper is coated with an insulating material such as enamel are wound.

[0020] [[ID=第十九]] The rotor 50 is disposed inside the stator 30 and coaxially with the stator 30. The rotor 50 is constituted by, for example, a laminated steel plate body formed by laminating a plurality of annular electromagnetic steel plates 511. An output shaft 70 is fitted (for example, press-fitted) into the center of the rotor 50.

[0021] On the rotor 50, a plurality of permanent magnets 53 are arranged (disposed) in a convex shape (arc shape) on the rotation axis side (inner side) when viewed from the rotation axis direction. In this embodiment, three permanent magnets 53 are provided per pole. Also, in this embodiment, the number of poles of the electric motor 10 is four poles.

[0022] More specifically, the rotor 50 has a rectangular cross-section cut perpendicular to the rotation axis and a plurality (12 in this embodiment) of magnet slots 52 extending in a columnar shape parallel to the rotation axis are formed at intervals along the circumferential direction. Here, in this embodiment, a configuration is adopted in which three arc-shaped magnet slots 52 are set as a set (one pole), and a total of four-pole magnet slots 52, that is, three-divided four-pole (12) magnet slots 52 are formed.

[0023] Each magnet slot 52 houses a permanent magnet 53. The permanent magnet 53 is formed, for example, in a substantially rectangular plate shape and is housed inside each of the plurality of magnet slots 52.

[0024] As the permanent magnet 53, for example, a rare earth magnet is preferably used. Examples of the rare earth magnet include a three-component neodymium magnet obtained by adding iron and boron to neodymium, and a samarium cobalt magnet composed of a two-component alloy of samarium and cobalt. Instead of the rare earth magnet, a ferrite magnet mainly made of iron oxide powder, an alnico magnet using aluminum, nickel, cobalt, etc. as raw materials may also be used.

[0025] Here, the electric motor 10 is cooled by a coolant such as oil (corresponding to the cooling medium described in the claims). In particular, the electric motor cooling structure 1 has the function of cooling the electric motor 10 more uniformly and thereby improving the cooling performance (cooling efficiency).

[0026] Therefore, each of the multiple electromagnetic steel sheets 511 that make up the rotor core 51 has multiple grooves 512 formed on one side in a substantially radial pattern, through which a coolant such as oil flows. In other words, the rotor core 51 is formed by stacking multiple electromagnetic steel sheets 511, each having multiple grooves 512 formed on one side in a substantially radial pattern, through which oil and the like flows.

[0027] Multiple grooves 512 can be formed, for example, by crushing (pressing). Here, if the thickness of the electromagnetic steel sheet 511 is, for example, about 0.25 to 3 mm, it is preferable that each groove 512 has, for example, a depth of about 0.1 mm and a width of 0.1 mm or more. It is preferable that the size (depth and width) of the grooves 512 be set considering the pressure loss of coolant such as oil.

[0028] Furthermore, the rotor core 51 has multiple through holes 513 that penetrate in the axial direction. Each through hole 513 is connected (in communication with) the ends of multiple grooves 512 that overlap when viewed from the axial direction. Therefore, the multiple grooves 512 are arranged (formed) between the inner circumferential surface of the rotor 50 (output shaft 70) and the through holes 513. Each through hole 513 collects coolant such as oil flowing in from each of the multiple grooves 512 and discharges it to the outside from both sides of the rotor core 51.

[0029] Furthermore, in order to supply (distribute) oil or the like to each groove 512 from the center of the output shaft 70, for example, grooves are formed on the outer surface (excluding both ends) of the output shaft 70 along the axial direction, facing the open ends of the grooves 512, and through holes are formed that penetrate radially through the bottom of the grooves and the hollow center.

[0030] Furthermore, in order to avoid interruption of the magnetic circuit by through-holes 513 that penetrate in the axial direction and to suppress deterioration of torque characteristics, etc., each through-hole 513 (and the multiple grooves 512) is arranged (formed) to avoid the magnetic circuit through which magnetic flux passes (or easily passes). More specifically, each through-hole 513 (and the multiple grooves 512) is arranged, for example, on the inside of the permanent magnet 53 when viewed from the direction of the rotation axis, and curved in a convex shape toward the rotation axis side (inward).

[0031] Furthermore, each of the multiple electromagnetic steel sheets 311 that make up the stator core 31 also has multiple grooves 312 formed on one side in a substantially radial pattern, through which a coolant such as oil flows. In other words, the stator core 31 is formed by stacking multiple electromagnetic steel sheets 311, each having multiple grooves 312 formed on one side in a substantially radial pattern, through which oil and the like flows.

[0032] Similar to the rotor core 51 described above, the multiple grooves 312 can be formed, for example, by crushing (pressing). Here, if the thickness of the electromagnetic steel sheet 311 is, for example, about 0.25 to 3 mm, it is preferable that each groove 312 has, for example, a depth of about 0.1 mm and a width of 0.1 mm or more. It is preferable that the size (depth and width) of the grooves 312 be set considering the pressure loss of coolant such as oil.

[0033] Furthermore, the stator core 31 has multiple through holes that penetrate in the axial direction, namely, multiple outer circumference through holes (distribution holes) 3131 and multiple inner circumference through holes 3132. When viewed from the direction of rotation axis, each outer circumference through hole (distribution hole) 3131 is located radially outward, and each inner circumference through hole 3132 is located radially inward. In addition, the outer circumference through holes (distribution holes) 3131 and the inner circumference through holes 3132 are arranged in pairs.

[0034] The outer circumference through hole (distribution hole) 3131 is connected (in communication) to one end of each of the multiple grooves 312 that overlap when viewed from the axial direction, and the inner circumference through hole 3132 is connected (in communication) to the other end of each of the multiple grooves 312 that overlap when viewed from the axial direction. Therefore, the multiple grooves 312 are arranged (formed) between the outer circumference through hole (distribution hole) 3131 and the inner circumference through hole 3132.

[0035] The outer peripheral through-hole (distribution hole) 3131 is, for example, divided (into two parts) approximately in the center, and both ends are closed. The outer peripheral through-hole (distribution hole) 3131 distributes, for example, a coolant such as oil supplied from outside the stator 30 to each of the multiple grooves 312.

[0036] The inner circumferential through-hole 3132 is, for example, divided (into two parts) approximately in the center, and both ends are open. The inner circumferential through-hole 3132 collects coolant such as oil flowing in from each of the multiple grooves 312 and discharges it to the outside from both sides of the stator 30 (stator core 31).

[0037] Furthermore, in order to avoid interruption of the magnetic circuit by the axially penetrating outer-circumferential through-holes (distribution holes) 3131 and inner-circumferential through-holes 3132, and to suppress deterioration of torque characteristics, each outer-circumferential through-hole (distribution hole) 3131 and each inner-circumferential through-hole 3132 (and the multiple grooves 312) are arranged (formed) to avoid the magnetic circuit through which magnetic flux passes (or easily passes). More specifically, each outer-circumferential through-hole (distribution hole) 3131 and each inner-circumferential through-hole 3132 (and the multiple grooves 312) are arranged (formed) for example, between adjacent stator windings (coils) 34 when viewed from the axial direction, and offset further to the outer circumference.

[0038] As described above, the rotor 50 is constructed (a flow path for oil, etc. is formed), that is, a rotor core 51 is formed by stacking multiple electromagnetic steel sheets 511, each having multiple grooves 512 formed substantially radially on one side for the flow of oil, etc., and the ends of multiple grooves 512 that overlap when viewed from the axial direction are connected to through holes 513 that penetrate in the axial direction. For example, oil supplied through the output shaft 70 (axis core) flows from the output shaft 70 into the multiple grooves 512, passes through the multiple grooves 512 (by hydraulic pressure and centrifugal force due to the rotation of the rotor 50), and is sent to each through hole 513 located on the outer circumference. The oil is then collected in each through hole 513 and discharged to the outside from both sides of the rotor 50.

[0039] As a result of the flow of oil or other coolant, the surface area over which the oil flows (contact area), i.e., the cooling area of ​​the rotor 50 (rotor core 51), is increased, allowing the rotor core 51 and the permanent magnets 53 to be cooled more uniformly and efficiently.

[0040] Furthermore, as described above, the stator 30 is constructed (a flow path for oil, etc. is formed), that is, a stator core 31 is formed by stacking multiple electromagnetic steel sheets 311, each having multiple grooves 312 formed substantially radially on one side for the flow of oil, etc., and one end of each of the multiple grooves 312 that overlap when viewed from the axial direction is connected to the outer peripheral through hole (distribution hole) 3131, and the other end is connected to the inner peripheral through hole 3132. For example, oil supplied from the outer circumference of the stator 30 flows from the outer circumference of the stator 30 into the outer peripheral through hole (distribution hole) 3131, is distributed to each of the multiple grooves 312 by the outer peripheral through hole (distribution hole) 3131, passes through the multiple grooves 312, and is sent to the inner peripheral through hole 3132. It is then collected in the inner peripheral through hole 3132 and discharged to the outside from both sides of the stator 30.

[0041] As a result of the flow of oil or other coolant, the surface area over which the oil flows (contact area), i.e., the cooling area of ​​the stator 30 (stator core 31), is increased, allowing the stator core 31 and stator windings 34 to be cooled more uniformly and efficiently.

[0042] As described in detail above, according to this embodiment, the rotor core 51 is formed by stacking multiple electromagnetic steel sheets 511, each having a plurality of grooves 512 through which oil or the like flows formed substantially radially on one surface. Therefore, the area over which oil or the like flows (contact area), i.e., the cooling area of ​​the rotor core 51, can be increased. Thus, the rotor core 51 can be cooled more uniformly and more efficiently. Similarly, the stator core 31 is formed by stacking multiple electromagnetic steel sheets 311, each having a plurality of grooves 312 through which oil or the like flows formed substantially radially on one surface. Therefore, the area over which oil or the like flows (contact area), i.e., the cooling area of ​​the stator core 31, can be increased. Thus, the stator core 31 can be cooled more uniformly and more efficiently.

[0043] As a result, the electric motor 10 can be cooled more uniformly (i.e., cooling with less temperature distribution bias can be achieved), thereby improving cooling performance (cooling efficiency).

[0044] Furthermore, since the permanent magnets 53 of the rotor 50 can be cooled efficiently, the operating temperature range of the permanent magnets 53 can be lowered. As a result, the output of the electric motor 10 can be increased, or if the output is kept the same, a permanent magnet with a lower heat resistance grade can be used, thereby reducing the cost of the electric motor 10. In addition, since the stator windings (coils) 34 of the stator 30 can be cooled efficiently, the operating temperature of the stator windings (coils) 34 is reduced, which reduces copper loss in the electric motor 10 and improves energy efficiency.

[0045] According to this embodiment, multiple through holes (outer circumference through hole (distribution hole) 3131, inner circumference through hole 3132, through hole 513) are formed to penetrate in the axial direction and are connected to the ends of multiple grooves 312, 512 that overlap when viewed from the axial direction, and are used to distribute oil or the like to each of the multiple grooves 312, 512, or to collect and discharge oil or the like from each of the multiple grooves 312, 512. Therefore, oil or other coolant can be efficiently supplied to and discharged from each of the multiple grooves 312, 512.

[0046] According to this embodiment, the outer-circumferential through-hole (distribution hole) 3131, the inner-circumferential through-hole 3132, the through-hole 513 (and the multiple grooves 312, 512) are arranged (formed) to avoid magnetic circuits through which magnetic flux passes (or easily passes). Therefore, the division of magnetic circuits by through-holes, etc., can be avoided, and deterioration of torque characteristics, etc., can be suppressed. In particular, by forming the grooves 312, 512 by crushing (pressing), the degree of freedom in the shape of the grooves 312, 512 (oil passages) can be increased, making it possible to avoid magnetic circuits more flexibly while ensuring cooling performance.

[0047] According to this embodiment, each through hole 513 (and the plurality of grooves 512) is arranged, for example, on the inside of the permanent magnet 53 when viewed from the direction of the rotation axis, and curved in a convex shape toward the rotation axis side (inward). Furthermore, each outer circumference through hole (distribution hole) 3131 and each inner circumference through hole 3132 (and the plurality of grooves 312) are arranged (formed) between adjacent stator windings 34 and offset toward the outer circumference when viewed from the axial direction. As a result, the division of the magnetic circuit by each outer circumference through hole (distribution hole) 3131 and each inner circumference through hole 3132 can be avoided, and deterioration of torque characteristics and the like can be suppressed.

[0048] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, the electromagnetic steel sheets 311 and 511 were laminated so that one surface with grooves 312 and 512 formed thereon faced the other surface without grooves 312 and 512. However, the electromagnetic steel sheets 311 and 511 may be laminated so that one surface faces the other surface and the other surface faces the other surface.

[0049] Furthermore, the number, shape, and size of the grooves 312 and 512 formed may be changed depending on, for example, the temperature distribution. That is, for example, in areas where the temperature is relatively high, the number of grooves 312 and 512 may be increased or their size may be increased compared to areas where the temperature is low. Also, for example, the shape of the grooves 312 and 512 may be changed to avoid the magnetic circuit.

[0050] Furthermore, the arrangement, number, and number of poles of the permanent magnets 53 attached to the rotor 50 shown in the above embodiment are illustrative examples and are not limited to the above embodiment. In addition, although the above embodiment described the case in which the present invention is applied to an interior permanent magnet (IPM) motor as an example, the present invention can also be applied to other types of electric motors (motors), such as surface permanent magnet (SPM) motors and induction motors (IM motors).

[0051] Furthermore, the dimensions, materials, and other specific numerical values ​​shown in the above embodiments are illustrative examples to facilitate understanding of the present invention and do not limit the present invention unless otherwise specified. [Explanation of Symbols]

[0052] 1. Cooling structure of electric motor 10 Electric motors 30 staters 31 Stator Core 311 Electrical steel sheet 312 groove 3131 Outer peripheral side through hole (distribution hole) 3132 Inner circumferential through hole 32 York 33 Teeth 34 Stator windings (coils) 50 rotors 51 Rotor Core 511 Electrical steel sheet 512 groove 513 Through hole 52 magnetic slots 53 Permanent Magnets 70 Output shaft

Claims

1. A rotor core formed by laminating multiple electromagnetic steel sheets, It comprises a stator core formed by laminating multiple electromagnetic steel sheets, A cooling structure for an electric motor, characterized in that each of the plurality of electromagnetic steel sheets constituting the rotor core and / or the plurality of electromagnetic steel sheets constituting the stator core has a plurality of grooves formed substantially radially through which a cooling medium flows.

2. The cooling structure for an electric motor according to claim 1, characterized in that the plurality of grooves are formed on one surface of each of the plurality of electromagnetic steel sheets.

3. The cooling structure for an electric motor according to claim 2, characterized in that it is formed to penetrate in the axial direction and is connected to the ends of each of the multiple grooves that overlap when viewed from the axial direction, and comprises multiple through holes for distributing a cooling medium to each of the multiple grooves, or for collecting and discharging a cooling medium from each of the multiple grooves.

4. The cooling structure for an electric motor according to claim 3, characterized in that the through-hole and the groove are arranged to avoid a magnetic circuit through which magnetic flux passes.

5. The cooling structure for an electric motor according to claim 4, characterized in that the through-hole and the groove are arranged between stator windings when viewed from the axial direction.

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