JP2011055654A - Cooling structure of electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling structure of an electric motor with improved cooling performance by improving thermal conductivity with assured electric insulation. <P>SOLUTION: A cooing structure of an electric motor M includes: a casing 1; a stator 3 having a coil 7; a rotor 2; and coil end covers 8 and 9 which are attached to coil ends 7a and 7b to allow an oil to be interposed between the cover and the coil ends 7a and 7b as well as the casing 1. The coil ends 7a and 7b are divided into an insulation unnecessary portion T which requires no electrical insulation against the casing 1 and an insulation necessary portion S which requires electrical insulation against the casing 1. When the coil end covers 8 and 9 are attached to the coil ends 7a and 7b, a part that faces the insulation unnecessary portion T is formed from a metal material having good thermal conductivity and an electrical insulation surface U of electrical insulation material having good electrical insulation is formed on the surface facing the insulation necessary portion S. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cooling structure for an electric motor, and more particularly to a cooling structure for an electric motor that cools the electric motor by releasing heat of a coil end to the outside.

  Electric motors are widely used as power sources for industrial machines and vehicles. Particularly, when used as a driving power source for vehicles, the motors are required to be small in size, high in output, or high in efficiency. In addition, when an electric motor is operated, heat is inevitably generated due to the action of an electric resistance, a magnetic field, and the like, so that the maximum output of the electric motor is often limited by an increase in the temperature of the electric motor. Therefore, in order to achieve high output or high efficiency of the motor, it is necessary to improve the cooling performance for suppressing the temperature rise of the motor.

  An example of a cooling structure for improving the cooling performance of such an electric motor is described in Patent Document 1. The motor cooling structure described in Patent Document 1 is a coil for removing heat from a coil end between a coil end and a motor case for the purpose of improving cooling efficiency for releasing heat generated from the motor. A cooling structure for cooling a motor provided with an end cover, in which a cooling liquid penetrates between the coil end cover and the coil end or between the coil end cover and the motor case. A liquid passage is formed. Further, this Patent Document 1 describes that the coil end and the motor case are reliably insulated by configuring the coil end cover with an insulating member having a thermal conductivity higher than a predetermined value.

  In Patent Document 2, for the purpose of improving the heat dissipation of the stator coil, a corrugated cross section made of copper is provided between the insulating resin layer provided on the outer periphery of the coil and the copper coil end cover and the housing. An invention relating to a motor configured to improve heat dissipation from a coil end cover of heat generated in a stator coil during operation by connecting a heat transfer spacer is described.

  Further, in Patent Document 3, for the purpose of improving the heat transfer cooling performance from the stator coil to the housing, the outer surface of the metal ring attached to the coil end of the stator coil is brought into close contact with the inner surface of the housing. Releasing heat from the metal ring while ensuring insulation between the coil end and the metal ring rather than installing an adhesive tape and filler as an electrical insulation member between the inner surface of the body and the surface of the coil end An invention relating to a rotating electrical machine configured to enhance the above is described.

  Patent Document 4 describes an invention related to an electric motor for the purpose of reducing the number of parts and the number of assembly steps. And this patent document 4 describes that the terminal cover which covers the external connection terminal which has the several lead wire taken out from the motor main-body part is formed with the rubber | gum which has waterproofness and electrical insulation. Has been.

  Patent Document 5 describes an invention relating to a stepping motor aimed at ensuring a sufficient insulation distance and creepage distance between a coil and a stator without requiring a resin sealing step. Patent Document 5 discloses a pair of stator yokes having pole teeth arranged on comb teeth, a coil wound around a bobbin body provided between the pair of stator yokes, and an insulating pressure-resistant cover. A structure in which a pressure-resistant cover composed of an outer lid pressure-resistant cover and an inner lid pressure-resistant cover is covered in a double manner so as to suppress creeping discharge between the stator yoke and the coil in an opening that does not enclose the coil of the bobbin main body. Is described.

JP 2009-118667 A Japanese Patent Laid-Open No. 10-290543 JP-A-6-70508 JP 2005-318742 A JP 2005-318788 A

  As described above, the motor inevitably generates heat during its operation, but the coil end is the main heat generating part. Since the coil end portion is provided with a terminal block and a neutral point that require electrical insulation with respect to the motor case, for example, as in the motor cooling structure described in Patent Document 1 above, the coil When a coil end cover for cooling the end is provided, the coil end cover has a thermal conductivity for efficiently transferring the heat of the coil end to the motor case and dissipating it to the outside, as well as a terminal block and neutral point. Electrical insulation is required to ensure electrical insulation between the motor case and the motor case.

  Therefore, in the motor cooling structure described in Patent Document 1, a minute gap through which the cooling liquid penetrates and a liquid passage through which the cooling liquid flows are formed between the coil end cover and the coil end or the motor case. At the same time, the coil end cover is formed of an insulating member having a predetermined thermal conductivity. As a result, according to the motor cooling structure described in Patent Document 1, the coil end cooling effect by the cooling liquid can be obtained while ensuring the electrical insulation between the motor case and the coil end. .

  However, specifically, the insulating member constituting the coil end cover as described above is assumed to be a member made of, for example, a resin having a predetermined thermal conductivity. However, the resin is generally good. Although it has electrical insulation, its thermal conductivity is only about 1/1000 to 1/100 of the thermal conductivity of metals such as iron, aluminum, and copper. It is inferior in sex. Therefore, when the coil end cover is formed of a resin insulating member, sufficient thermal conductivity can be ensured for more efficiently releasing the heat of the coil end to the outside through the coil end cover. Therefore, sufficient cooling performance for cooling the coil end could not be obtained. As described above, there is still room for improvement in order to improve the cooling performance of the electric motor by satisfying both the thermal conductivity and electric insulation of the coil end cover to be mounted for cooling the coil end.

  The present invention has been made paying attention to the above technical problem, and while ensuring the necessary electrical insulation between the coil end and the motor case, the thermal conductivity between them is improved to improve the electric motor. An object of the present invention is to provide a cooling structure for an electric motor capable of improving the cooling performance.

  In order to achieve the above object, an invention according to claim 1 includes a stator housed in a casing and fixed and formed with a coil, and a rotor supported by the casing so as to be rotatable relative to the stator. A coil end which is attached to a coil end portion from which the coil protrudes at both end portions in the rotation axis direction of the rotor of the stator so that a cooling liquid is interposed between the coil end portion and the inner wall of the casing. In the cooling structure of an electric motor including a cover, the coil end portion is divided into an insulation unnecessary portion that does not require electrical insulation with respect to the casing and an insulation necessary portion that requires electrical insulation with respect to the casing. When the coil end cover is attached to the coil end portion, the portion facing the insulation-unnecessary portion is thermally conductive. It is characterized in that the electrically insulating the surface facing the good is formed of a metallic material and said insulating requiring portion is electrically insulated surface formed consisting of good electrical insulating materials.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the electrically insulating surface is formed on the basis of a spatial distance and a creepage distance that require electrical insulation of the portion requiring insulation. To do.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, when the coil end cover is attached to the coil end portion, a magnetic insulating member having a good magnetic insulation property in a portion close to the rotor. A magnetic insulating surface made of is further formed.

  According to the first aspect of the present invention, when installing a coil end cover for interposing a cooling liquid between the coil end portion and the inner wall of the casing in order to release the heat of the coil end portion to the outside, In the end part, the insulation-unnecessary part and the insulation-necessary part are separated, and the coil end cover is formed with an electrically insulating surface only in a part facing the insulation-needed part, so that the coil-end part is insulated from the insulation-necessary part. Electrical insulation is established between the coil end cover and between the coil-needed portion and the casing. And the part which opposes the insulation unnecessary part in a coil end cover, ie, the part which does not need to electrically insulate the coil end part in a coil end cover, is formed with a metal material with good heat conductivity. Therefore, it is possible to improve the cooling performance of the electric motor by increasing the thermal conductivity when transferring the heat generated in the coil end portion to the outside of the casing while ensuring the electric insulation of the necessary part of insulation by the electric insulation surface. .

  According to the invention of claim 2, when an electrical insulation surface is formed on the coil end cover, the electrical insulation surface is formed based on a spatial distance and a creepage distance that require electrical insulation of a portion requiring insulation. A range is set. That is, the electrical insulation surface of the coil end cover is formed so as to include both the range of the spatial distance and the range of the creepage distance that are necessary to electrically insulate the necessary part of insulation. For this reason, the electrically insulating surface of the coil end cover can be formed in a necessary and sufficient range. As a result, the other portions of the coil end cover except the electrically insulating surface can be formed of a metal material having good thermal conductivity, and heat generated in the coil end portion can be transmitted to the outside of the casing via the coil end cover. The thermal conductivity of can be increased as much as possible.

  According to the invention of claim 3, the magnetic insulating surface is formed in the portion of the coil end cover that is close to the rotor. When installing the coil end cover on the coil end part of the stator, if the part of the coil end cover that is close to the rotor is made of a material with high magnetic permeability, such as iron, it will be affected by the leakage magnetic flux from the rotor. Coil end cover will generate heat. Therefore, according to the third aspect of the present invention, by forming the magnetic insulating surface as described above, it is possible to eliminate the influence of the leakage magnetic flux from the rotor and prevent the coil end cover from generating heat.

It is sectional drawing for demonstrating the structure of the cooling structure of the electric motor which concerns on this invention. It is a schematic diagram for demonstrating the structure of the coil end cover especially with the cooling structure of the electric motor shown in FIG. It is a schematic diagram for demonstrating the insulation required site | part of a coil end part by the cooling structure of the electric motor shown in FIG.

  Next, an embodiment of the present invention will be described with reference to the drawings. First, FIG. 1 shows the configuration of an electric motor (motor) M that is a subject of the present invention. The motor M is a device that generates power by using electric energy. For example, the motor M is a power generation device that generates driving torque of driving wheels as a driving force source of a vehicle. In FIG. 1, a motor M is housed in a casing 1 and is fixed to the casing 1, and a stator 2 is housed in the casing 1 and supported by the casing 1 so as to be relatively rotatable with respect to the stator. 3 is provided.

  Specifically, the casing 1 is composed of a motor case 1a and a motor case cover 1b, and the motor case 1a and the motor case cover 1b are made of a metal material such as an aluminum alloy, for example. The motor case 1a is formed with an internal space in which the rotor 2 and the stator 3 can be accommodated. With the rotor 2 and the stator 3 being accommodated in the internal space, a disk-like shape is formed from the outside (left side in FIG. 1). The motor case cover 1b is fixed by, for example, bolt fastening.

  The rotor 2 is fixed integrally with the rotary shaft 6 on the outer peripheral portion of the rotary shaft 6 rotatably supported by the motor case 1a and the motor case cover 1b by bearings 4 and 5. The rotor 2 and the rotating shaft 6 are accommodated and arranged in an inner peripheral portion of a stator 3 to be described later. Therefore, the rotor 2 is supported on the casing 1 by the bearings 4 and 5 so as to be rotatable relative to the stator 3.

  The stator 3 is formed in a cylindrical shape capable of accommodating the rotor 2 in the inner peripheral portion, and is arranged so that the inner peripheral surface and the outer peripheral surface of the rotor 2 are separated from each other by a predetermined distance in the radial direction. It is fixed to the case 1a. Further, the stator 3 is formed with a coil 7 in which a conducting wire is wound around a stator core (not shown) arranged in a circumferential direction integrally with the stator 3. The coil 7 is formed of, for example, enamel-coated wire, and is fixed to the stator core by being molded or coated with resin or the like.

  The portions 7a and 7b in which the coil 7 protrudes at both ends of the rotor 3 of the stator 3 in the axial direction of the rotor 2 (in the left-right direction in FIG. 1), that is, the coil end portion. Coil end covers 8 and 9 are attached to 7a and 7b. The coil end covers 8 and 9 are formed in an annular shape so as to cover the coil end portions 7 a and 7 b of all the coils 7 arranged in the circumferential direction of the stator 3.

  These coil end covers 8, 9 are respectively arranged between the coil end portion 7a and the motor case cover 1b and between the coil end portion 7b and the motor case 1a after the motor case cover 1b is fixed to the motor case 1a. Are not fixed to the coil end portions 7a and 7b, the motor case 1a or the motor case cover 1b, and between the coil end portion 7a and the motor case cover 1b, and The coil end portion 7b and the motor case 1a are sandwiched and supported.

  As described above, in order to improve the maximum output and efficiency of the motor M, it is necessary to improve the cooling performance for suppressing the temperature rise of the motor M. In order to improve the cooling performance of the motor M, it is effective to suppress the heat generation of the coil end portions 7a and 7b which are the main heat generating portions of the motor M. Therefore, in the motor M of the present invention, flow paths 8a, 8b, and 9a for guiding the cooling liquid for cooling the coil end portions 7a and 7b are formed in the coil end covers 8 and 9, respectively.

  Specifically, each flow path 8a, 8b, 9a is formed on the surface of the coil end covers 8, 9, that is, the surface facing the coil end portion 7a of the coil end cover 8, the surface facing the motor case cover 1b, and the coil end. By the spaces respectively formed by the grooves respectively formed on the surface facing the coil end portion 7b of the cover 9, and the outer surface of the coil end portion 7a, the inner wall surface of the motor case cover 1b, and the outer surface of the coil end portion 7b. It is configured. For example, as shown in FIG. 2, the flow paths 8 a, 8 b, and 9 a are annularly formed along the coil end portions 7 a and 7 b of all the coils 7 aligned in the circumferential direction of the annular stator 3. .

  Each flow path 8a, 8b, 9a is connected to a flow system (not shown) including a pump, a flow path and the like for circulating the cooling liquid, and is connected to each flow path 8a, 8b, 9a. Each is supplied with a cooling liquid, and the cooling liquid flows through each of the flow paths 8a, 8b, and 9a. As the cooling liquid, for example, oil such as vehicle engine oil or automatic transmission ATF (automatic transmission fluid) can be used.

  As described above, the coil end covers 8, 9 are supported by being sandwiched between the coil end portion 7a and the motor case cover 1b or between the coil end portion 7b and the motor case 1a. Therefore, between the coil end cover 8 and the motor case cover 1b, between the coil end cover 8 and the coil end portion 7a, between the coil end cover 9 and the motor case 1a, and between the coil end cover 9 and Minute gaps P, Q, and R are formed between the coil end portions 7b.

  Accordingly, since the flow paths 8a, 8b, and 9a are communicated with the minute gaps P, Q, and R, oil is supplied as a cooling liquid to the flow paths 8a, 8b, and 9a. Then, the oil leaks into the minute gaps P, Q, R, and the oil is interposed in the minute gaps P, Q, R. The intervals between the minute gaps P, Q, and R are set to such a magnitude that a capillary phenomenon occurs when liquid enters the minute gaps P, Q, and R, thereby allowing the respective flow paths 8a, 8b. , 9a can be effectively filled in the entire micro gaps P, Q, and R.

  In this way, by passing the cooling oil through the flow paths 8a, 8b, 9a formed between the coil end covers 8, 9 and the coil end portions 7a, 7b and the casing 1, a minute gap P is obtained. , Q, R are filled with oil. That is, the air existing between the coil ends 7a, 7b and the coil end covers 8, 9 and between the coil end cover 8 and the casing 1 is expelled and oil is interposed. As a result, the heat generated in the coil end portions 7a and 7b can be released to the outside using oil flowing through the flow paths 8a, 8b and 9a as a medium, and the cooling performance of the coil end portions 7a and 7b is improved. be able to. Further, in the minute gaps P, Q, and R, air that has a high heat insulating effect is replaced and cooling oil is interposed, so that between the coil end portions 7a and 7b and the coil end covers 8 and 9, and the coil The thermal conductivity between the end cover 8 and the casing 1 is improved, and the cooling performance of the coil end portions 7a and 7b can be further improved.

  On the other hand, as shown in FIG. 1 and FIG. 3, for example, as shown in FIGS. Therefore, it is necessary to electrically insulate the neutral point 10 and the terminal block 11 from the outside of the casing 1 and the like. Accordingly, the parts that are in contact with or close to the necessary insulation parts such as the neutral point 10 and the terminal block 11 are formed of an electrically insulating material having good electrical insulation, or are covered with an electrically insulating member made of an electrically insulating material. It is necessary to take measures.

  That is, the coil end covers 8 and 9 that are in contact with or in close proximity to the necessary insulation points such as the neutral point 10 and the terminal block 11 need to be formed of an electrically insulating material, or the surface must be covered with an electrically insulating member. is there. In this case, as the electrical insulation material, resin or rubber generally has good electrical insulation properties. For example, the coil end covers 8 and 9 are made of resin, or a member made of resin. By covering the surface, the electrical insulation of the neutral point 10 and the terminal block 11 can be ensured. On the other hand, an electrical insulating member such as resin or rubber has poor thermal conductivity as compared with, for example, a metal member. Therefore, for example, by forming the coil end covers 8 and 9 using resin as a material, the coil end portion 7a is formed. , 7b, and the heat conductivity when the heat is released to the outside through the coil end covers 8, 9 is reduced.

  Therefore, in the cooling structure for the motor M according to the present invention, the coil end portions 7a and 7b are not required to be electrically insulated from the casing 1, and the insulation is required to be electrically insulated from the casing 1. A metal material having a good thermal conductivity at a portion facing the insulation unnecessary portion of the coil end portions 7a and 7b when the coil end covers 8 and 9 are attached to the coil end portions 7a and 7b. The portions of the coil end portions 7a and 7b that face the necessary insulation portions are made of an electrically insulating material having good electrical insulation, so that the electrical insulation properties and thermal conductivity of the coil end covers 8 and 9 can be reduced. And the cooling performance of the cooling structure can be improved.

  Specifically, as shown in FIG. 3, the spatial distance and creepage distance that require electrical insulation with respect to the neutral point 10 and the terminal block 11 provided in the coil end portions 7a and 7b are taken into consideration. In addition, a necessary part S for insulation is set. By setting the necessary insulation portion S in the coil end portions 7a and 7b, the other portions of the coil end portions 7a and 7b excluding the necessary insulation portion S are set as the unnecessary insulation portion T.

  As shown in FIG. 2 (a), when the coil end covers 8, 9 are attached to the coil end portions 7a, 7b, electrical insulation is provided on the surface of the coil end covers 8, 9 facing the necessary insulation portion S. A surface U is formed. In other words, the electrical insulation surface U is formed on the coil end covers 8 and 9 so as to include both the range of the spatial distance and the range of the creepage distance that are necessary to electrically insulate the site S requiring insulation. .

  In short, the electrical insulation surface U only needs to be electrically insulated in a range that takes into account the spatial distance and creepage distance of the portions of the coil end covers 8 and 9 that face the insulation required portion S. If only the portion including the electrical insulation surface U in the circumferential direction of the coil end covers 8 and 9 in the circumferential direction of the coil end covers 8 and 9 is formed of an electrical insulation material having good electrical insulation properties such as resin, for example. Good. Alternatively, the electric insulating surface U is formed as an insulating layer made of an electric insulating material by, for example, applying resin or spraying ceramics such as alumina only on the range of the electric insulating surface U on the surfaces of the coil end covers 8 and 9. It may be formed.

  In addition, as shown in FIG. 1, when the neutral point 10 exists in the inner peripheral side (left side in the example of FIG. 1) of the coil end cover 9, for example, it is necessary to electrically insulate the neutral point 10 The range of the creeping distance, that is, the electrical insulating surface U, may be set so as to extend from the inner peripheral side to the outer peripheral side (right side in the example of FIG. 1) of the coil end cover 9.

  On the other hand, when the coil end covers 8 and 9 are attached to the coil end portions 7a and 7b, the portions of the coil end covers 8 and 9 that face the insulation-required portion S, that is, the above-described electrical insulating surfaces in the coil end covers 8 and 9 Other portions except the portion where U is formed are formed of a metal material having good thermal conductivity such as an aluminum alloy. That is, in the coil end covers 8 and 9 in the motor M of the present invention, the range that requires electrical insulation with respect to the necessary insulation sites S such as the neutral point 10 and the terminal block 11 is set to the minimum necessary by the electrical insulation surface U. In addition, a portion formed of a metal material having good thermal conductivity corresponding to the insulation unnecessary portion T of the coil end portion 7 is set as wide as possible. Therefore, the heat generated in the coil end portions 7a and 7b can be released to the outside through the coil end covers 8 and 9 as efficiently as possible.

  Further, in the cooling structure of the motor M according to the present invention, for example, as shown in FIG. 2B, when the coil end covers 8 and 9 are attached to the coil end portions 7a and 7b, they are close to or opposed to the rotor 2. A magnetic insulating surface V made of a magnetic insulating member having a good magnetic insulating property is formed on the portion to be formed. As described above, since the leakage magnetic flux exists around the rotor 2, if a member made of a material having a high magnetic permeability such as iron is disposed in the vicinity of the rotor 2, the high permeability is provided. The magnetic susceptibility member generates heat due to the influence of the leakage magnetic flux of the rotor 2. Therefore, by forming the magnetic insulating surface V on the coil end covers 8 and 9 as described above, it is possible to eliminate the influence of leakage magnetic flux from the rotor 2 and prevent the coil end covers 8 and 9 from generating heat. it can.

  As described above, according to the cooling structure of the motor M according to the present invention, in order to release the heat generated in the coil end portions 7a and 7b to the outside, the coil end portions 7a and 7b and the inner wall of the casing 1 When installing coil end covers 8 and 9 for interposing cooling oil or the like between them, the coil end portions 7a and 7b are divided into a portion T that does not require insulation and a portion S that requires insulation. 8 and 9 are formed with an electrical insulating surface U only in a portion facing the necessary insulation portion S. Therefore, the insulation required part S of the coil end parts 7a and 7b and the coil end covers 8 and 9 and the insulation required part S of the coil end parts 7a and 7b and the casing 1 are surely electrically insulated. be able to.

  The portions of the coil end covers 8 and 9 that face the insulation-unnecessary portion T, that is, the portions that do not need to electrically insulate the coil end portions 7a and 7b of the coil end covers 8 and 9 have good thermal conductivity. It is formed of a metal material. Therefore, while ensuring the electrical insulation of the insulation required part S by the electrical insulation surface U, the thermal conductivity at the time of transferring the heat generated in the coil end portions 7a and 7b to the outside of the casing 1 is increased, and as a result. The cooling performance of the motor M can be improved.

  In the above-described specific example, the cooling structure of the motor M according to the present invention has coil end covers 8 and 9 for interposing cooling oil or the like between the coil end portions 7a and 7b and the inner wall of the casing 1. For example, without using the coil end covers 8 and 9, the coil end portions 7a and 7b are brought into direct contact with the casing 1, and the heat generated in the coil end portions 7a and 7b is converted into the casing. The cooling structure of the motor M according to the present invention can be applied to the configuration in which the coil end portions 7a and 7b are cooled by being transmitted to 1 and discharged to the outside. That is, in that case, the above-described specific example is formed by forming the electrical insulation surface U set as described above only on the portion of the casing 1 that faces the insulation required portion S of the coil end portions 7a and 7b. The same actions and effects can be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Casing, 1a ... Motor case, 1b ... Motor case cover, 2 ... Rotor, 3 ... Stator, 6 ... Rotating shaft, 7 ... Coil, 7a, 7b ... Coil end part, 8, 9 ... Coil end cover, S ... Insulation required part, T ... Insulation unnecessary part, U ... Electrically insulating surface, V ... Magnetic insulating surface, M ... Motor (motor)

Claims (3)

A stator housed in a casing and fixed and formed with a coil, a rotor supported by the casing so as to be relatively rotatable with respect to the stator, and the coil at both ends of the stator in the rotation axis direction In the cooling structure of the electric motor provided with a coil end cover that is attached to the protruding coil end part and interposes a cooling liquid between the coil end part and the inner wall of the casing,
The coil end portion is divided into an insulation-unnecessary portion that does not require electrical insulation with respect to the casing, and an insulation-necessary portion that requires electrical insulation with respect to the casing.
When the coil end cover is attached to the coil end portion, the portion facing the portion that does not require insulation is formed of a metal material having good thermal conductivity, and the surface facing the portion requiring insulation is electrically insulating. An electric motor cooling structure in which an electric insulating surface made of a good electric insulating material is formed.   The cooling structure for an electric motor according to claim 1, wherein the electrical insulation surface is formed based on a spatial distance and a creepage distance that require electrical insulation of the part requiring insulation.   2. The coil end cover according to claim 1, further comprising a magnetic insulating surface made of a magnetic insulating member having a good magnetic insulating property at a portion close to the rotor when the coil end cover is attached to the coil end portion. 3. A cooling structure for an electric motor according to 1 or 2.

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