JP2016049005A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor with a simplified structure for cooling the inside of a housing.SOLUTION: In a rotor core 6, a rotor core side flow passage 60 of which one end is opened in an upper space of a housing 1 is formed in an axial direction, In a low plate 7 that is provided at a lower side of the rotor core 6, a plate side flow passage 70 of which one end is opened is formed in a lower end of the rotor core side flow passage 60. In an outer peripheral part of a shaft 5 lower than the lower plate 7, a cylindrical body 4 of which the lower end side is immersed in a coolant is provided. Between an inner peripheral surface of the cylindrical body 4 and an outer peripheral surface of the shaft 5, a cylindrical body side flow passage 40 of which the lower end is opened in a coolant accommodation space 10 and the upper end is opened in the plate side flow passage 70 is formed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric motor.

Electric motors are used in construction machines and other machines. As an electric motor, there is a vertical electric motor in which an annular stator core is provided in a housing, and a rotor is rotatably disposed along the inner periphery of the stator core along the vertical direction.
Among the vertical electric motors, there is a type that cools a stator core, a rotor, and the like in a housing with a cooling fluid.

As a rotor of a vertical motor that cools a stator core, a rotor, and the like, there is a conventional example including a shaft that is pivotally supported by a housing, a rotor core that is fitted to the shaft, and plates that are fitted to the top and bottom of the shaft ( Patent Document 1).
In Patent Document 1, a flow path for sending cooling oil sent from an external hydraulic power source to the shaft is formed in the housing, and flow paths communicating with the flow path of the housing are provided in the axial direction and the radial direction of the shaft. A flow path communicating with the flow path of the shaft is formed in the lower plate, and a flow path communicating with the flow path of the plate is formed extending up and down the rotor core. The cooling oil sent from the outside to the flow path of the rotor core is injected from the injection holes formed in the upper plate, and falls toward the bottom of the housing while cooling the stator coil of the stator core.

JP 2012-5289 A

In Patent Document 1, in order to cool the inside of the housing, cooling oil is sent from an external hydraulic power source to flow paths provided in the housing and the rotor, and is formed in an upper plate through the flow path. The jetting holes are jetted onto the stator core.
Therefore, in the conventional example of Patent Document 1, there is a problem that a structure for sending cooling oil to the inside becomes complicated.

  The objective of this invention is providing the electric motor which simplified the structure which cools the inside of a housing.

  An electric motor of the present invention includes a housing having a bottom portion and a cylindrical portion provided at a peripheral portion of the bottom portion, in which a cooling fluid storage space for storing a cooling fluid is formed, and an annular shape along the inner periphery of the cylindrical portion A stator core that is disposed and provided with a coil; and a rotor that is rotatably disposed in an inner circumferential space of the stator core. And a ring-shaped lower plate provided at a lower end portion close to the bottom portion of the rotor core, and the cooling fluid is circulated in the axial direction of the rotor core and one end thereof A rotor core side flow path opened in a space opposite to the bottom is formed so as to penetrate, and the lower plate has a plate side flow path having one end opened at the other end of the rotor core side flow path. A cylindrical body having at least one end immersed in the cooling fluid is provided on an outer peripheral portion of the shaft closer to the bottom than the lower plate, and an inner peripheral surface of the cylindrical body and an outer periphery of the shaft A cylindrical body-side flow path having one end opened to the cooling fluid storage space and the other end opened to the other end of the plate-side flow path is formed between the surface and the cylindrical body-side flow path. It has a flow path main body which becomes small as the width dimension with the outer peripheral surface goes to the bottom from the lower plate.

  In this invention, the said cylindrical body has a fitting part fitted with the said shaft, and the said cylindrical body side flow path is formed between the said fitting part and the said shaft, and the said flow-path main body and the said It is preferable to have a communication path that communicates with the plate-side flow path.

  In the present invention, the flow channel main body has a cylindrical outer peripheral surface having the same dimensions along the axial direction of the shaft, and a tapered shape in which the radial dimension decreases from the lower plate to the bottom of the cylindrical body. Preferably, it is formed between the inner peripheral surface.

  In the present invention, the tapered inner peripheral surface is preferably formed continuously in the circumferential direction.

  In the present invention, the communication path is formed between a fitting inner peripheral surface having the same diameter dimension in the axial direction of the fitting portion and a recess formed along the axial direction on the outer periphery of the shaft. It is preferable that

  According to the present invention, the lower plate is provided on the outer peripheral edge of the fitting plate portion, the fitting plate portion fitting with the shaft, and the outer end of the lower plate is in contact with the end surface of the rotor core and the outer periphery is formed with a concave portion. The plate-side flow path is formed along the axial direction in the inner peripheral portion of the fitting plate portion facing the shaft, and is communicated with the communication path; and the first flow A configuration is preferable in which a path and the rotor core side flow path are communicated to each other and a second flow path formed by a space between the concave portion of the outer peripheral edge portion, the fitting plate portion, and an end surface of the rotor core is preferable.

In the electric motor of the present invention, when the coil provided in the stator core is energized, the shaft provided with the rotor core rotates. When the cylindrical body rotates at a high speed together with the shaft, the cooling fluid stored in the housing moves in the housing in the same direction as the rotation of the cylindrical body due to its viscosity.
The cooling fluid is sucked from an opening at one end of the tubular body side flow path formed between the tubular body and the shaft. Since the cylindrical body side flow path has a flow path body whose width dimension with the outer peripheral surface of the shaft decreases from the lower plate toward the bottom, the centrifugal force of the cooling fluid accompanying the rotation of the shaft is larger on the lower plate side than on the bottom side. Thus, the suction force from the end of the cylindrical body side flow path becomes large.
And a cooling fluid is sent to the plate side flow path of a lower plate through a cylindrical body side flow path. The cooling fluid sent to the plate-side flow path is sent to the rotor core-side flow path, during which the rotor core is directly cooled and discharged from the opening into the housing. As the shaft rotates at a high speed, the cooling fluid becomes a mist state and is sprayed on the upper portion of the stator and the upper portion of the rotor at a position away from the cooling fluid storage space. The cooling fluid sprayed on the stator or the like flows down and returns to the cooling fluid storage space.
Thus, in this invention, a cylindrical body will have a function of a pump with a shaft, and the cooling fluid in a cooling fluid storage space is the cylindrical body side flow path formed between the cylindrical body and the shaft. Then, the air is injected into the housing through the plate-side flow path formed in the lower plate and the rotor core-side flow path formed in the rotor core, and cooling inside the housing is self-completed in the housing.
Therefore, in the present invention, since it is not necessary to install the fluid supply source outside the housing, the cooling structure inside the housing can be simplified.

Sectional drawing which shows the electric motor concerning one Embodiment of this invention. The front view of a shaft. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. The top view of a rotor core. The top view of a lower plate. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. Sectional drawing of a cylindrical body. The top view of a cylindrical body.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[General configuration of electric motor]
FIG. 1 shows the entire electric motor of this embodiment.
In FIG. 1, an electric motor is provided in a housing 1, a stator 2 disposed in an annular shape inside the housing 1, a rotor 3 disposed rotatably in an inner circumferential space of the stator 2, and the rotor 3. This is a vertical electric motor including a cylindrical body 4.
[housing]
The housing 1 includes a substantially disk-shaped bottom portion 11, a cylindrical portion 12 having one end provided at the peripheral edge of the bottom portion 11, and a lid portion 13 provided at the other end of the cylindrical portion 12. A lower space inside the housing 1 is a cooling fluid storage space 10 that stores a cooling fluid. In the present embodiment, the cooling fluid is a cooling oil having a predetermined viscosity.
The cylindrical portion 12 has a water jacket 14, and the housing 1 is cooled as water flows from an external fluid source to the flow path 14 </ b> A. In the present embodiment, it is not always necessary to provide the water jacket 14.

[Stator]
The stator 2 includes an annular stator core 20 formed by laminating a number of electromagnetic steel plates (not shown) along the axial direction.
The stator core 20 includes a yoke 21 on the outer peripheral side that is continuous in the circumferential direction, and a plurality of teeth 22 that protrude from the yoke 21 toward the central rotor 3 and extend in the axial direction. The plurality of teeth 22 are provided at equal intervals along the circumferential direction of the yoke 21. Coils 24 are wound around the teeth 22.
In the present embodiment, the stator core 20 may be composed of a plurality of divided core units. That is, the split core is mounted on each insulator, and an electromagnetic coil is wound around each of the insulators to form a split core unit. A plurality of divided core units are arranged on the inner periphery of the cylindrical portion 12 so as to form an annular shape, and these divided core units are electrically connected.

[Outline of rotor]
The rotor 3 is close to the bottom 11 of the rotor core 6, the shaft 5 whose ends are pivotally supported by the bearings 50 on the bottom 11 and the lid 13, the cylindrical rotor core 6 provided on the outer periphery of the shaft 5. A ring-shaped lower plate 7 provided at the end portion and a ring-shaped upper plate 8 provided at the end portion close to the lid portion 13 of the rotor core 6 are provided.
[shaft]
The structure of the shaft 5 will be described with reference to FIGS.
FIG. 2 shows the front of the shaft 5. FIG. 3 shows a cross section along the radial direction of the shaft 5.

2 and 3, the shaft 5 includes a shaft main body 51, a flange portion 52 provided on the lower end side of the shaft main body 51, a lower end portion 53 provided on the lower end side of the shaft main body 51, and the shaft main body 51. And an upper end portion 54 provided on the upper end side. The lower end 53 and the upper end 54 are each supported by a bearing 50 (see FIG. 1).
The shaft body 51 has a locking groove 51 </ b> A for locking the rotor core 6 formed along the axial direction.
The flange portion 52 has an outer diameter larger than the outer diameter of the shaft body 51, and a plurality of (four in FIG. 3) concave portions 52A are formed at equal intervals along the axial direction on the outer peripheral surface. . These recesses 52 </ b> A form communication paths 40 </ b> A together with the inner peripheral surface of the cylindrical body 4. As will be described later, the communication path 40A is a flow path for circulating the cooling fluid stored in the cooling fluid storage space 10 of the housing 1. In the present embodiment, the number of recesses 52A is not limited to four, and may be eight, for example. In addition, although the concave portion 52A is illustrated as an example of a rectangle, the shape is not limited, and may be, for example, a U-shape.

[Rotor core]
Returning to FIG. 1, the rotor core 6 is an annular member formed by laminating a large number of electromagnetic steel plates along the axial direction.
The planar shape of the rotor core 6 is shown in FIG.
In FIG. 4, locking protrusions 6 </ b> A that are locked to the locking grooves 51 </ b> A of the shaft 5 are formed on the inner peripheral portion of the rotor core 6.
A plurality (16 in FIG. 4) of embedded holes 6B are formed in the rotor core 6 along the circumferential direction. A prismatic permanent magnet 6M is embedded in each of the embedded holes 6B.

The embedded hole 6B of the rotor core 6 is provided in a V shape so as to be symmetric when viewed from the axial center side. A pair of such embedded holes 6B is taken as one set, and one magnetic pole is formed by a pair of permanent magnets 6M embedded in the set of embedded holes 6B. That is, the number of poles of the rotor 3 of this embodiment is eight. The polarities of adjacent magnetic poles are different from each other. The magnetic poles are formed at equal intervals along the circumferential direction of the rotor core 6. The adjacent embedded holes 6B are V-shaped with their ends connected to each other.
A rotor core side flow path 60 is formed by being surrounded by a pair of permanent magnets 6 </ b> M at portions connected to each other in the adjacent embedded holes 6 </ b> B. The rotor core side flow path 60 circulates the cooling fluid sent from the communication path 40 </ b> A toward the interior upper space of the housing 1, and one end thereof is opened to the upper space located on the side opposite to the bottom portion 11. (See FIG. 1).

[Lower plate]
The structure of the lower plate 7 is shown in FIGS. FIG. 5 shows a plan view of the lower plate 7, and FIG. 6 shows a cross section of the lower plate 7.
5 and 6, the lower plate 7 has a fitting plate portion 71 that fits with the shaft main body 51.
The lower surface of the lower plate 7 is in contact with the upper end surface of the flange portion 52 of the shaft 5 (see FIG. 1). A concave groove 71A is formed on the inner peripheral surface of the lower plate 7 so as to penetrate vertically. The grooves 71A constitute the first flow path 701 together with the outer peripheral surface of the shaft main body 51, and are formed at four locations at equal intervals along the circumferential direction.

The outer peripheral portion of the lower plate 7 is formed with a concave portion 72A on the inner periphery. The concave portion 72A is formed continuously with the groove 71A.
The number of the concave portions 72A corresponding to the concave grooves 71A (four locations in the figure) is formed.
The planar shape of the recessed portion 72A includes a tangential portion 721 that includes the planar shape of the groove 71A and extends in the tangential direction of the outer peripheral surface of the shaft main body 51, and extends in the radial direction of the shaft main body 51 from the end of the tangential portion 721. And a radial portion 722 including a flow channel 60. In the present embodiment, since the two adjacent rotor core-side flow paths 60 are communicated with one concave portion 72A, the radial direction portions 722 are provided at both ends of the tangential portion 721, respectively.

The inner peripheral surface of the lower plate 7 is in contact with the outer peripheral surface of the shaft body 51.
The upper end surface of the outer peripheral edge 72 is in contact with the lower end surface of the rotor core 6.
A second flow path 702 is configured by a space surrounded by the inner peripheral surface of the concave portion 72 </ b> A, the lower end surface of the rotor core 6, and the upper surface of the fitting plate portion 71. The upper end of the second flow path 702 is opened to the rotor core side flow path 60. The lower end of the second channel 702 is opened to the first channel 701. That is, the second flow path 702 communicates with the first flow path 701 and the rotor core side flow path 60. In the present embodiment, the plate-side channel 70 is configured by the first channel 701 and the second channel 702.

[Upper plate]
Returning to FIG. 1, the upper plate 8 fixes the rotor core 6 together with the lower plate 7. The upper plate 8 is a ring-shaped member whose inner peripheral portion is fixed to the upper portion of the shaft body 51.
A window portion 8 </ b> A is formed in the upper plate 8 so as to correspond to the opening of the rotor core side channel 60. The window portion 8 </ b> A is larger than the opening of the rotor core side channel 60 without blocking the opening of the rotor core side channel 60 so that the upper end of the rotor core side channel 60 is opened to the upper space of the housing 1. Is formed.

[Cylinder]
The structure of the cylindrical body 4 is shown in FIGS. FIG. 7 shows a cross section of the cylindrical body 4, and FIG. 8 shows a plane of the cylindrical body 4.
7 and 8, the cylindrical body 4 includes a fitting portion 41 that fits with the flange portion 52 of the shaft 5, and a main body that is integrally formed with the fitting portion 41 and has a lower end close to the bottom portion 11. Part 42.
The fitting part 41 supports the cylindrical body 4 in a cantilever shape. A fitting inner peripheral surface 41 </ b> A for fitting the outer peripheral portion of the flange portion 52 is formed in the fitting portion 41. The fitting inner peripheral surface 41A constitutes the communication path 40A together with the recess 52A.
The main body 42 has a tapered inner peripheral surface 42A having a diameter that decreases in the direction from the flange 52 to the bottom 11 (downward in FIG. 7), and a cylindrical outer peripheral surface 42B having the same dimensions from the bottom 11 to the flange 52. And have.
The tapered inner peripheral surface 42A is formed continuously in the circumferential direction.

In FIG.1 and FIG.7, it is immersed in the cooling fluid from the lower end edge nearest to the bottom part 11 of the main-body part 42 to the middle position.
Between the tapered inner peripheral surface 42A of the main body 42 and the outer peripheral surface of the shaft 5, a flow path main body 40B having a lower end opened in the cooling fluid storage space 10 and an upper end opened in the communication path 40A is formed. .
The flow channel main body 40B has the same flow channel shape as the cross-sectional shape of the main body portion. That is, the flow path body 40 </ b> B becomes smaller in width from the outer peripheral surface of the shaft 5 toward the bottom 11 from the lower plate.
The flow channel main body 40B and the communication passage 40A communicate with each other, and the cylindrical body side flow channel 40 of the present embodiment is constituted by these.

[Method of cooling the inside of the motor]
Next, a method for cooling the inside of the housing 1 of the electric motor according to the present embodiment will be described.
The cooling fluid is stored in the cooling fluid storage space 10 of the housing 1. In a state where the cooling fluid is stored, the lower end portion of the cylindrical body 4, the lower end portion of the coil 24 of the stator 2, and the bearing 50 provided on the bottom portion 11 are immersed in the cooling fluid.
The coil 24 is energized for the operation of the electric motor. Then, the shaft 5, the rotor core 6, the lower plate 7, the upper plate 8, and the cylindrical body 4 rotate together.
Since the cylindrical body 4 is immersed in the cooling fluid from the middle position to the lower end edge, the cooling fluid stored in the cooling fluid storage space 10 moves in the same direction as the cylindrical body 4 rotates at a high speed. In other words, the liquid level of the cooling fluid is lowest at the center of the cooling fluid storage space 10 and becomes higher according to the outer periphery.

Since the width dimension of the flow channel main body 40B of the cylindrical body side flow channel 40 decreases from the lower plate 7 toward the bottom 11, the cooling fluid has a large suction force from the lower end to the upper end of the flow channel main body 40B due to the action of centrifugal force. Will be sucked. In other words, the tubular body 4 and the shaft 5 function as a pump, and the cooling fluid is sucked into the tubular body side flow path 40 formed therebetween.
The cooling fluid flowing upward through the flow path body 40B passes through the communication passage 40A formed between the flange portion 52 of the shaft 5 and the fitting portion 41 of the cylindrical body 4, and the plate of the lower plate 7 It is sent to the side channel 70. The cooling fluid sent to the plate-side flow path 70 is sent to the rotor core-side flow path 60 and discharged from the upper end opening of the rotor core-side flow path 60 toward the upper space inside the housing 1.

The cooling fluid discharged from the upper end opening of the rotor core-side flow path 60 becomes a mist state when the rotor core 6 rotates at a high speed together with the shaft 5, and becomes a mist state on the upper part of the coil 24 of the stator 2, the upper part of the rotor core 6, and the lid part 13. It will be sprayed on the bearing 50 provided.
The cooling fluid sprayed on the coil 24 or the like of the stator 2 flows down and returns to the cooling fluid storage space 10.
By continuing such a process, the cooling of the inside of the housing 1 is completed by the operation of the electric motor.

[Effect of the embodiment]
In the electric motor having the above-described configuration, the rotor core 6 is formed with the rotor core side flow path 60 having one end opened in the upper space of the housing 1 along the axial direction, and the lower plate 7 provided below the rotor core 6 is provided with the rotor core. A plate-side flow path 70 having one end opened at the lower end of the side flow path 60 is formed, and a cylindrical body 4 having a lower end side immersed in a cooling fluid is provided on the outer peripheral portion below the lower plate 7 of the shaft 5. A cylindrical body side channel 40 having a lower end opened in the cooling fluid storage space 10 and an upper end opened in the plate side channel 70 was formed between the inner peripheral surface of the cylindrical body 4 and the outer peripheral surface of the shaft 5. Therefore, the cooling fluid in the cooling fluid storage space 10 of the housing 1 is jetted into the upper space inside the housing 1 through the cylindrical body side channel 40, the plate side channel 70, and the rotor core side channel 60, thereby cooling the inside of the housing 1. Will be self-contained within the housing. Therefore, since it is not necessary to separately install the fluid supply source outside the housing 1, the cooling structure inside the housing can be simplified.

  Since the fitting portion 41 of the cylindrical body 4 is fitted to the shaft 5, the cylindrical body 4 rotates without being displaced from the shaft 5, and the cooling fluid is reliably transmitted from the opening at one end of the cylindrical body side flow path 40. Can be aspirated. In addition, since the communication path 40A communicating with the flow path main body 40B is formed between the fitting portion 41 and the shaft 5, the plate from the flow path main body 40B can be used even when the fitting portion 41 is engaged with the shaft 5. A cooling fluid can be circulated through the side channel 70.

  Since the flow path body 40B is formed between the cylindrical outer peripheral surface of the shaft 5 and the tapered inner peripheral surface 42A of the cylindrical body 4, the shaft 5 itself can be made common with the structure of the conventional shaft. In addition, the flow path body 40B can be formed by a simple method of forming a taper inside the cylindrical body 4.

Since the tapered inner peripheral surface 42A is continuously formed in the circumferential direction, the configuration of the flow path body 40B can be simplified.
By forming the communication passage 40A between the fitting inner peripheral surface 41A of the fitting portion 41 and the concave portion of the shaft 5, the configuration of the communication passage 40A can be simplified.
The lower plate 7 has a configuration in which an outer peripheral edge portion in which a concave portion is formed on the outer peripheral edge of the fitting plate portion 71 is provided, and the plate-side flow path 70 is arranged on the inner peripheral portion facing the shaft 5 of the fitting plate portion 71. Since it has the 1st flow path 701 formed along the direction and the 2nd flow path 702 formed in the space of the inner peripheral part of a concave part, the fitting board part 71, and the end surface of the rotor core 6, it is a plate side flow path. 70 can have a simple structure.

[Modification]
It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the above-described embodiment, the tubular body 4 is fitted with the fitting portion 41 that fits with the flange portion 52 of the shaft 5.
The cylindrical body side flow path 40 has a communication path 40A formed between the fitting part 41 and the flange part 52. However, in the present invention, when the communication path 40A is provided, the shaft 5 is provided. It is not always necessary to provide the flange portion 52. For example, a ring-shaped portion in which the communication passage 40A is formed may be provided integrally with the fitting portion 41 instead of the flange portion.

The present invention can be used for electric motors in construction machines and other machines.

  DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Stator, 3 ... Rotor, 4 ... Cylindrical body, 5 ... Shaft, 6 ... Rotor core, 7 ... Lower plate, 8 ... Upper plate, 10 ... Cooling fluid storage space, 11 ... Bottom part, 12 ... Tube , 20 ... stator core, 24 ... coil, 40 ... cylindrical body side flow path, 40A ... communication path, 40B ... flow path main body, 41 ... fitting part, 41A ... fitting inner peripheral surface, 42 ... main body part, 42A ... Tapered inner peripheral surface, 51 ... shaft body, 52 ... collar part, 53 ... lower end part, 54 ... upper end part, 60 ... rotor core side flow path, 70 ... plate side flow path, 71 ... fitting plate part, 701 ... first flow Road, 702 ... second flow path

Claims (6)

A housing having a bottom portion and a cylindrical portion provided at a peripheral portion of the bottom portion, in which a cooling fluid storage space for storing a cooling fluid is formed, and an annularly disposed coil along the inner periphery of the cylindrical portion is provided. A stator core, and a rotor rotatably disposed in the inner circumferential space of the stator core,
The rotor includes a shaft pivotally supported on the bottom portion, a cylindrical rotor core provided on an outer peripheral portion of the shaft, and a ring-shaped lower plate provided on a lower end portion of the rotor core adjacent to the bottom portion. Have
In the axial direction of the rotor core, the cooling fluid is circulated and a rotor core side flow path having one end opened to a space opposite to the bottom portion is formed therethrough,
The lower plate is formed with a plate-side flow path having one end opened at the other end of the rotor core-side flow path,
A cylindrical body having at least one end immersed in the cooling fluid is provided on the outer peripheral portion of the shaft closer to the bottom than the lower plate,
Between the inner peripheral surface of the cylindrical body and the outer peripheral surface of the shaft, a cylindrical body-side flow path having one end opened to the cooling fluid storage space and the other end opened to the other end of the plate-side flow path. Formed,
The cylindrical body-side flow path has a flow path body whose width dimension with the outer peripheral surface of the shaft decreases from the lower plate toward the bottom. The electric motor according to claim 1,
The tubular body has a fitting portion that fits with the shaft, and the tubular body side channel is formed between the fitting portion and the shaft, and the channel body and the plate side channel. An electric motor having a communication path communicating with the motor. The electric motor according to claim 1 or 2,
The flow path body includes a cylindrical outer peripheral surface having the same dimension along the axial direction of the shaft, and a tapered inner peripheral surface having a radial dimension that decreases from the lower plate to the bottom of the cylindrical body. An electric motor formed between the two. The electric motor according to claim 3,
The electric motor characterized in that the tapered inner peripheral surface is formed continuously in the circumferential direction. In the electric motor according to any one of claims 2 to 4,
The communication path is formed between a fitting inner peripheral surface having the same diameter dimension in the axial direction of the fitting portion and a recess formed along the axial direction on the outer periphery of the shaft. An electric motor characterized by The electric motor according to any one of claims 2 to 5,
The lower plate includes a fitting plate portion that is fitted to the shaft, and an outer peripheral edge portion that is provided on an outer peripheral edge of the fitting plate portion, an end portion of which is in contact with an end surface of the rotor core, and a concave portion is formed on an inner periphery thereof. Have
The plate-side flow path includes a first flow path formed along an axial direction in an inner peripheral portion of the fitting plate portion facing the shaft and communicated with the communication path, the first flow path, and the rotor core-side flow path. And a second flow path formed in a space between the concave portion of the outer peripheral edge portion, the fitting plate portion, and the end face of the rotor core.