Patent Description:
Electric motors may be installed in home appliances such as a cleaner, a hair dryer, and the like.

A cleaner or a hair dryer may generate rotational force by using an electric motor as a power source.

For example, an electric motor may be fastened to a fan. The fan may generate airflow by being rotated as driving force is applied from the electric motor.

A handy stick cleaner or a hair dryer is operated while a user directly holds it by hand.

In order to enhance user portability and convenience, there is a need to reduce size and weight of a cleaner or a hair dryer.

In order to reduce a weight of a fan motor of a cleaner, it is preferable to use a plastic material, instead of a metal material, as a material for producing a housing.

However, in the case of the plastic material, a heat transfer coefficient (thermal conductivity) is lowered to <NUM>/<NUM> to <NUM>/<NUM> compared to an existing metal material. The housing that is made of the plastic material to surround a bearing hinders heat dissipation of the bearing.

As a result, in the bearing housing made of the plastic material, a temperature of the bearing is increased by <NUM> or more, compared to a bearing housing made of a metal material, thereby shortening the lifespan of the bearing and reducing reliability of the fan motor.

In order to solve the problems, a heat sink that has a shape exposed to the air while surrounding a bearing and is made of a material having high thermal conductivity is required.

When a plastic housing is injected, a heat sink made of a metal material may be inserted into the housing so that the housing and the heat sink can be integrally injected.

However, when the heat sink is manufactured by the insert-injection in the plastic housing, it is difficult to secure an alignment of the heat sink, which may cause misalignment between bearings on both sides during operation of the fan motor.

Therefore, a heat dissipation structure that has a self-aligning function capable of adjusting (aligning) concentricity between bearings while reducing a temperature of the bearings is required.

On the other hand, a plurality of bearings rotatably support a rotational shaft. Such bearings may have a double-side bearing support structure and a one-side bearing support structure depending on positions of the bearings disposed on a rotational shaft.

<FIG> is a conceptual view for explaining a problem caused in the case where a misalignment of concentricity (axial misalignment) between bearings on both sides occurs in the double-side bearing support structure.

(a) of <FIG> illustrates a case in which an axial alignment is made between a first bearing 2a and a second bearing 2b and concentricity between the both bearings is normal. (b) of <FIG> illustrates a case where the concentricity between the both bearings is abnormal due to axial misalignment between the first bearing 2a and the second bearing 2b.

In the double-side bearing support structure, the plurality of bearings 2a and 2b are mounted on both sides of a rotational shaft <NUM> with a rotor <NUM> (or permanent magnet) interposed therebetween. Since the double-side bearing support structure supports the rotor <NUM>, which includes the permanent magnet having a relatively heavy weight, on both sides of the rotational shaft <NUM>, it is advantageous in view of stably supporting the shaft.

However, when the concentricity alignment (axial alignment) between the bearings 2a and 2b is not offered, wear occurs due to friction between the rotational shaft <NUM> and the bearings 2a and 2b.

In the one-side bearing support structure, a plurality of bearings are mounted on one side (a single side) of the rotor <NUM> (or permanent magnet) or one side of the rotational shaft <NUM>.

The one-side bearing support structure requires only one housing surrounding the bearings. This is more advantageous for miniaturization and weight reduction of the fan motor, and has no concern about misalignment between the bearings and the rotational shaft <NUM>.

However, the one-side bearing support structure has a limitation in stably supporting the rotational shaft <NUM> because the plurality of bearings are located on the one side of the rotational shaft <NUM>.

Prior Art Patent Document <CIT>; hereinafter, referred to as Patent Document <NUM>) discloses a disk-shaped heat sink having a larger diameter than an impeller to reduce temperatures of bearings, and a plurality of legs radially extending from one end of the heat sink.

The impeller and a rotor core are mounted on both ends of a rotational shaft. A plurality of bearings are disposed between the impeller and the rotor core to support the rotational shaft.

However, Patent Document <NUM> discloses a one-side bearing support structure in which the plurality of bearings are disposed on one side of the rotor core having a relatively heavy weight, and there is a limit to stably supporting the rotational shaft.

In addition, Patent Document <NUM> does not disclose a separate device for offering an axial alignment between the bearings.

Prior Art Patent Document <CIT>; hereinafter, referred to as Patent Document <NUM>) discloses an electric motor having a heat dissipation structure for bearings.

A can surrounds a bearing housing and acts as a heat dissipation fin (or heat sink).

Heat of a ball bearing which is generated during operation of the motor is dissipated to the outside of a casing cover sequentially through a ball bearing housing, a can, a motor casing, and the casing cover.

However, Patent Document <NUM> discloses a one-side bearing support structure in which one bearing is disposed on one side of a rotor core and thus supports only one side of a rotational shaft. As a result, it is difficult to expect stable support of the rotational shaft.

In addition, Patent Document <NUM> has a problem in that friction between the bearing and the rotational shaft occurs if the one side of the rotational shaft on which the single bearing is mounted and another side to which the rotor core is mounted are axially misaligned with each other.

<CIT> discloses a motor having an elastic mesh which is disposed between a bearing and a bearing housing for adjustable axial alignment and effective cooling of bearings.

The fan motor defined in the appended independent claim solves the above-identified problems.

A first aspect is to provide a fan motor having a heat dissipation fin that has a self-aligning function so as to improve axial alignment between bearings respectively supporting both sides of a rotational shaft.

A second aspect is to provide a fan motor having a heat dissipation fin that is capable of reducing temperatures of bearings by increasing an area exposed to air when a plastic housing is used to reduce a weight of the fan motor.

A third aspect is to provide a fan motor having a structure that is capable of increasing a support force for bearings by disposing a heat dissipation fin made of a metal material within a mold and enlarging a contact area between the heat dissipation fin and a plastic-injection surface when injecting plastic.

A fourth aspect is to provide a fan motor having a structure that is capable of significantly contributing to weight reduction of the motor by using a plastic housing.

A fifth aspect is to provide a fan motor having a structure that is capable of reducing an axial length of the fan motor as well as securing an insulation distance between a metal heat dissipation fin and a coil.

As a result of intensive research, the inventors of the present disclosure can achieve solution to the problems of the present disclosure and the aforementioned first to fifth aspects by the following embodiments of the present disclosure.

According to an embodiment of the present disclosure, the following effects can be provided.

First, a heat dissipation fin includes an inner ring part enclosing a bearing, an outer ring part surrounding the inner ring part, and a connection part connecting the outer ring part and the inner ring part. When a rotational shaft is obliquely disposed due to misalignment of concentricity of the bearing in a double-side bearing support structure, the inner ring part can be elastically deformed according to an inclination of the rotational shaft, thereby improving axial alignment of the bearing. In addition, an occurrence of wear due to friction between the bearing and the rotational shaft can be minimized.

Second, the heat dissipation fin includes heat dissipation expansion ribs that extend radially from an outer circumferential surface of the outer ring part. This can increase an area exposed to air even though using a casing and a housing that are made of a plastic material for reducing a weight of a fan motor of a cleaner, thereby lowering a temperature of the bearing.

Third, the heat dissipation fin is accommodated inside a second bearing housing, and the heat dissipation expansion ribs of the heat dissipation fin are coupled to second bridges extending from the second bearing housing to an inner circumferential surface of a second housing. When the heat dissipation pin is integrally manufactured with the bearing housing through insert-injection into a mold during plastic injection, support strength for the bearing can be increased.

Fourth, a shroud, a first housing, a second housing, a first bearing housing, and a second bearing housing, etc. that define the exterior of the fan motor can be made of a plastic material, which can significantly contribute to reducing a weight of the motor.

Fifth, an insulation cover is disposed between the coil of a stator and the heat dissipation fin made of a metal material, so as to secure an insulation distance between the coil and the heat dissipation fin and shorten an axial distance between the coil and the heat dissipation fin, thereby reducing an axial length of the fan motor.

Hereinafter, a fan motor according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

In the following description, in order to clarify the characteristics of the present disclosure, descriptions of some components may be omitted.

It will be understood that when an element is referred to as being "connected with" another element, the element can be connected with the another element or intervening elements may also be present. In contrast, when an element is referred to as being "directly connected with" another element, there are no intervening elements present.

A singular representation used herein may include a plural representation unless it represents a definitely different meaning from the context.

The term "fan motor" used in the following description may be understood as a concept meaning a device that suctions or blows air by rotating a fan using power of an electric motor or the like.

The term "radial" used in the following description means a shape extending like spokes from a central point in all directions.

The term "self-alignment" used in the following description means that an inclination of a surface surrounding a bearing is automatically adjusted according to an inclination of a shaft.

The term "thrust" used in the following description means a force applied by a fluid such as air to an impeller in a direction opposite to an axial direction when the impeller suctions the fluid in the axial direction, namely, a force acting on the impeller or a rotational shaft on which the impeller is mounted.

The term "axial direction" used in the following description means a longitudinal direction of the rotational shaft.

The term "radial direction" used in the following description means a longitudinal direction of a line segment from a center of a circle or cylinder to a point on a circumference.

The term "circumferential direction" used in the following description means a direction of a circumference of a circle.

The terms "upper side", "lower side", "right side", "left side", "front side" and "rear side" used in the following description will be understood through the coordinate system shown in <FIG>.

The term "axial direction" used in the following description may be understood as a concept corresponding to a vertical or up-down direction.

The term "radial direction" used in the following description may be understood as a concept corresponding to a left-right direction or a forward-backward direction.

The casing defines appearance of the fan motor. The casing includes a shroud <NUM>, a first housing <NUM>, and a second housing <NUM>. The casing may be formed of a plastic material.

The shroud <NUM> has an accommodation space in which the impeller <NUM> and vanes <NUM> are accommodated. The shroud <NUM> defines a boundary isolating outside and inside of the fan motor. Movement paths of air generated by the impeller <NUM> may be formed between the shroud <NUM> and the impeller <NUM> and between the shroud <NUM> and a vane hub <NUM> to be described later.

The shroud <NUM> is formed in a cylindrical shape. However, the shroud <NUM> may vary in diameter along a longitudinal direction of the cylinder.

Explaining a detailed configuration of the shroud <NUM>, the shroud <NUM> may include an inlet port <NUM>, curved portions <NUM> and <NUM>, an inclined portion <NUM>, a linear portion <NUM>, a radial extension portion <NUM>, and a coupling portion <NUM>. The detailed configuration of the shroud <NUM> may be divided in an order from an upstream side to a downstream side of the shroud <NUM> based on an air flow direction.

The inlet port <NUM> is located at an end portion of the upstream side of the shroud <NUM>. The inlet port <NUM> is formed in a cylindrical shape. The inlet port <NUM> has relatively small diameter and short length compared to other components of the shroud <NUM>. The inlet port <NUM> may be formed through the shroud <NUM> in an axial direction. One end portion of the impeller <NUM> may be accommodated inside the inlet port <NUM>.

Accordingly, air generated by the impeller <NUM> is suctioned through the inlet port <NUM>.

The inclined portion <NUM> is disposed at a downstream side of the inlet port <NUM>. The inclined portion <NUM> is inclined with respect to a rotational shaft <NUM> so that its diameter gradually increases from the upstream side to the downstream side of the shroud <NUM>.

The curved portions <NUM> and <NUM> may include a first curved portion <NUM> and a second curved portion <NUM>. The first curved portion <NUM> is formed in a curved shape having a preset first curvature to connect the inlet port <NUM> and the inclined portion <NUM>. The second curved portion <NUM> is formed in a curved shape having a preset second curvature to connect the inclined portion <NUM> and the linear portion <NUM>.

The first curved portion <NUM> and the second curved portion <NUM> may be curved in opposite directions to each other. The first curvature and the second curvature may be different from each other.

The linear portion <NUM> has a larger diameter than the inclined portion <NUM>. The linear portion <NUM> is formed in a cylindrical shape. A plurality of vanes <NUM> to be described later may be coupled to be in contact with an inner circumferential surface of the linear portion <NUM>.

The radial extension portion <NUM> extends in a radial direction between the linear portion <NUM> and the coupling portion <NUM>.

The rotational shaft <NUM> is disposed in a center of the casing. The rotational shaft <NUM> extends along the axial direction passing through the center of the casing.

One end portion of the rotational shaft <NUM> is accommodated inside the shroud <NUM>. The impeller <NUM> is rotatably mounted on the one end portion of the rotational shaft <NUM>.

The impeller <NUM> includes a hub <NUM> and a plurality of blades <NUM>.

The hub <NUM> is inclined so that its diameter increases along the axial direction. The diameter of the hub <NUM> gradually increases from an upstream-side end portion to a downstream-side end portion of the hub <NUM> based on an air flow direction.

A shaft through-hole is formed through the hub <NUM> in the axial direction such that the one end portion of the rotational shaft <NUM> is inserted through a central portion of the hub <NUM>.

Each of the plurality of blades <NUM> may spirally extend along the axial direction of the hub <NUM>. One end portion of the blade <NUM> may protrude radially from one axial end of the hub <NUM>. Another end portion of the blade <NUM> may protrude from another axial end of the hub <NUM> in the axial direction.

The plurality of blades <NUM> are spaced apart from one another at preset intervals along a circumferential direction of the hub <NUM>.

With the configuration, the impeller <NUM> can rotate together with the rotational shaft <NUM>. As the plurality of blades <NUM> rotate at high speed together with the hub <NUM>, air moves in an inner space of the shroud <NUM> and thereby external air can be suctioned.

The vanes <NUM> are disposed on an outer circumferential surface of the vane hub <NUM>.

The vane hub <NUM> may be formed in a cylindrical shape. The vane hub <NUM> may have a diameter which is larger than a maximum diameter of the hub <NUM>. A length of the vane hub <NUM> may be shorter than the diameter of the vane hub <NUM>.

The vane <NUM> may be provided in plurality. The plurality of vanes <NUM> are disposed on an outer circumferential surface of the vane hub <NUM> to be spaced apart from one another in the circumferential direction. The plurality of vanes <NUM> protrude radially outward from the outer circumferential surface of the vane hub <NUM>. The plurality of vanes <NUM> may be inclined into a curved shape with a preset curvature.

A bending (inclination) direction of the vane <NUM> may be opposite to a bending (inclination) direction of the blade <NUM>. For example, based on the air flow direction, the blades <NUM> may be inclined in a clockwise direction while the vanes <NUM> may be inclined in a counterclockwise direction.

The vanes <NUM> are configured to switch the air flow direction from the radial direction to the axial direction. Accordingly, air generated by the impeller <NUM> can be guided by the vanes <NUM> to flow in the axial direction.

A bearing through-hole may be formed through a central portion of the vane hub <NUM> so that a first bearing housing 152a, which will be described later, is inserted therethrough. The central portion of the vane hub <NUM> surrounds the first bearing housing 152a inserted through the bearing through-hole.

A first recess <NUM> may be formed to be recessed in one surface of the vane hub <NUM> in the axial direction. The first recess <NUM> is formed to surround a rim and a lower surface of the vane cover <NUM>.

The vane cover <NUM> may be inserted into the first recess <NUM> to cover an upper surface of the vane hub <NUM>. A height of the rim of the vane cover <NUM> may correspond to a recessed depth of the vane hub <NUM> in the axial direction.

Accordingly, an upper surface of the rim of the vane cover <NUM> can be flush with the upper surface of the vane hub <NUM>, thereby minimizing flow resistance of air when the air suctioned through the inlet port <NUM> flows from the impeller <NUM> to the vanes <NUM>.

A second recess <NUM> may be formed to be recessed in one surface of the vane cover <NUM> in the axial direction. An outer end portion of the hub <NUM> is accommodated in the second recess <NUM>. The second recess <NUM> is formed to surround a rim and a lower surface of the hub <NUM> at preset intervals in the axial and radial directions.

An upper surface of the outer lower end portion of the hub <NUM> can be flush with the upper surface of the rim of the vane cover <NUM> based on a bottom surface of the second recess <NUM>, thereby minimizing flow resistance of air when the air suctioned through the inlet port <NUM> flows from the impeller <NUM> to the vanes <NUM>.

A stopper accommodating hole <NUM> may be formed in the central portion of the vane cover <NUM> such that a stopper <NUM> to be described later is inserted therein. The central portion of the vane cover <NUM> surrounds the stopper <NUM> inserted in the stopper accommodating hole <NUM>.

A plurality of fastening holes <NUM> and <NUM> may be formed through the vane cover <NUM> and the vane hub <NUM> in an axial direction, respectively. The plurality of first fastening holes <NUM> formed through the vane cover <NUM> and the plurality of second fastening holes <NUM> formed through the vane cover <NUM> overlap each other in the axial direction. The plurality of first and second fastening holes <NUM> and <NUM> are spaced apart in the circumferential direction.

A first fastening member <NUM> such as a screw is fastened to the vane cover <NUM> and the vane hub <NUM> through the first fastening hole <NUM> and the second fastening hole <NUM>. Accordingly, the vane cover <NUM> and the vane hub <NUM> can be fastened to each other.

Accommodation grooves <NUM> may be formed in a bottom surface of the vane cover <NUM> so that screw heads of the first fastening members <NUM> are accommodated therein.

An outer diameter of each of the plurality of vanes <NUM> that radially protrude from the outer circumferential surface of the vane hub <NUM> may correspond to an inner diameter of the linear portion <NUM> of the shroud <NUM>. Accordingly, outer ends of the plurality of vanes <NUM> can be press-fitted to an inner circumferential surface of the linear portion <NUM> of the shroud <NUM>.

In addition, the vane hub <NUM> may be fixed to the shroud <NUM> by the plurality of vanes <NUM>, and coupled to the first bearing housing 152a to enclose the first bearing housing 152a, so as to support the first bearing housing 152a.

The rotational shaft <NUM> is disposed inside the shroud <NUM> to be rotatable relative to the shroud <NUM>.

The bearing <NUM> is provided to rotatably support the rotational shaft <NUM>. The bearing <NUM> may be provided in plurality.

The plurality of bearings <NUM> may include a first bearing 151a and a second bearing 151b.

The first bearing 151a and the second bearing 151b are spaced apart from each other on both sides of the rotational shaft <NUM> with a motor unit to be described later interposed therebetween.

A first bearing support portion is provided on one side of the rotational shaft <NUM>. A second bearing support portion is provided on another side of the rotational shaft <NUM>.

An impeller support portion is provided on one end portion of the rotational shaft <NUM>. The first bearing support portion may have the same diameter as the impeller support portion.

A rotor support portion is provided on the rotational shaft <NUM>. The rotor support portion may be formed to extend in the axial direction between the first bearing support portion and the second bearing support portion.

Diameters of the first bearing support portion and the second bearing support portion are smaller than that of the rotor support portion.

The first step jaw may be formed between the first bearing support portion and the rotor support portion, to restrict the first bearing 151a from moving toward the rotor <NUM> in the axial direction.

A second step jaw may be formed between the second bearing support portion and the rotor support portion, to restrict the second bearing 151b from moving toward the rotor <NUM> in the axial direction.

The following description of the bearing <NUM> may be applied to each of the first bearing 151a and the second bearing 151b, unless otherwise specified.

The bearing <NUM> may be implemented as a ball bearing <NUM>. The ball bearing <NUM> is provided to support a radial load of the rotational shaft <NUM>. The bearing <NUM> may include an outer ring, an inner ring, a plurality of balls, and a plurality of covers.

The outer ring is formed in a cylindrical shape. The bearing housing <NUM> may be formed to enclose the outer ring. The inner ring is formed in a cylindrical shape. The inner ring is disposed inside the outer ring to surround the bearing support portion.

The plurality of balls are disposed between the outer ring and the inner ring. The plurality of balls are spaced apart from one another at preset intervals in the circumferential direction of the outer ring and the inner ring.

The plurality of balls roll in contact with the outer ring and the inner ring between the outer ring and the inner ring. The inner ring rotates relative to the outer ring by the balls. The inner ring rotates together with the rotational shaft <NUM>.

The plurality of covers are coupled to cover both sides of the outer ring and the inner ring in the axial direction, respectively.

With the configuration, the plurality of bearings <NUM> can stably and rotatably support both sides of the rotational shaft <NUM>.

The bearing housing <NUM> is formed in a cylindrical shape. A bearing accommodating hole is formed through a central portion of the bearing housing <NUM> in the axial direction. The bearing <NUM> is accommodated in the bearing housing <NUM> through the bearing accommodating hole.

A first bearing housing 152a accommodates and encloses the first bearing 151a. A second bearing housing 152b accommodates and encloses the second bearing 151b.

The first housing <NUM> is fixedly inserted into the shroud <NUM>.

The first housing <NUM> is disposed at a downstream side of the vane <NUM> based on the air flow direction.

The first housing <NUM> includes a first bearing housing 152a, a plurality of first bridges <NUM>, and a first coupling ring <NUM>.

The first bearing housing 152a is disposed inside the first coupling ring <NUM>. The first coupling ring <NUM> is formed in a ring shape. An outer diameter of the first coupling ring <NUM> is formed to correspond to an inner diameter of a coupling portion <NUM> of the shroud <NUM>.

The first coupling ring <NUM> may be press-fitted to an inner circumferential surface of the coupling portion <NUM> of the shroud <NUM>. The first coupling ring <NUM> is fixed to an inner circumferential surface of the shroud <NUM>.

An inner diameter of the first coupling ring <NUM> is larger than a diameter of the first bearing housing 152a. The first bearing housing 152a is disposed inside the first coupling ring <NUM>.

The plurality of first bridges <NUM> extend radially between an inner circumferential surface of the first coupling ring <NUM> and an outer circumferential surface of the first bearing housing 152a. An outer end portion of each of the first bridges <NUM> is connected to the first coupling ring <NUM>, and an inner end portion of the first bridge <NUM> is connected to the first bearing housing 152a.

A flow guide <NUM> is formed on the inner circumferential surface of the first coupling ring <NUM>. The flow guide <NUM> is made to guide a flow direction of air that has passed through the vanes <NUM> to the inside of the motor unit.

The flow guide <NUM> is formed in a curved shape with a preset curvature.

The flow guide <NUM> protrudes radially from the inner circumferential surface of the first coupling ring <NUM>.

One axial end of the flow guide <NUM> comes into contact with the radial extension portion <NUM>. An inner diameter of the one axial end of the flow guide <NUM> may correspond to an inner diameter of the linear portion <NUM>.

Another axial end of the flow guide <NUM> comes into contact with one axial end of the second housing <NUM> to be described later. An inner diameter of the another axial end of the flow guide <NUM> may correspond to an inner diameter of the one axial end of the second housing <NUM>.

An inner diameter of the radial extension portion <NUM> may be larger than the inner diameter of the one axial end of the second housing <NUM>, based on the inner circumferential surface of the coupling portion <NUM>.

A radial protrusion length of the another axial end of the flow guide <NUM> may be larger than a radial protrusion length of the one axial end of the flow guide <NUM>.

The inner circumferential surface of the flow guide <NUM> has an arcuate cross-section. The inner diameter of the flow guide <NUM> may gradually decrease from the one axial end to the another axial end of the flow guide <NUM>.

The inner circumferential surface of the flow guide <NUM> connects the linear portion <NUM> to the one axial end of the second housing <NUM>.

With the configuration, the flow guide <NUM> can minimize flow resistance of air that has passed through the vanes <NUM>.

The first bridges <NUM> are disposed at the downstream side of the vane hub <NUM> based on the air flow direction. The first bridges <NUM> may be fastened to the vane hub <NUM>.

A first fastening groove <NUM> is formed in an inner end portion of each of the first bridges <NUM>. The first fastening groove <NUM> is disposed to overlap a first fastening hole <NUM> of the vane cover <NUM> and the second fastening hole <NUM> of the vane hub <NUM> in the axial direction. The first fastening member <NUM> such as a screw is fastened to the first fastening groove <NUM> through the first and second fastening holes <NUM> and <NUM>.

Accordingly, the first bridge <NUM> and the vane hub <NUM> are coupled to each other.

As the impeller <NUM> rotates, external air is suctioned in a first axial direction from the inlet port <NUM> toward the coupling portion <NUM>. At this time, the suctioned air applies a thrust that is as strong as a suction force of the impeller <NUM> to the impeller <NUM> and the rotational shaft <NUM> in a second axial direction opposite to the first axial direction.

The first bearing 151a may be moved in the second axial direction, which is opposite to an air suction direction, by the thrust applied to the rotational shaft <NUM>.

To solve this problem, a stopper <NUM> is disposed on one axial end of the first bearing housing 152a. The stopper <NUM> extends radially from the one axial end of the first bearing housing 152a so as to cover the one axial end of the first bearing 151a.

A shaft through-hole is formed through a central portion of the stopper <NUM> in the axial direction. The shaft through-hole has a diameter that is slightly larger than the diameter of the rotational shaft <NUM>.

According to this, the stopper <NUM> can restrict the first bearing 151a from moving in the second axial direction due to the thrust.

The thrust acting on the rotational shaft <NUM> is transferred to the first housing <NUM> through the first bearing 151a, the first bearing housing 152a, the first bridge <NUM>, and the first coupling ring <NUM>.

The first housing <NUM> may be referred to as a load-side housing in that it is located on one side of the rotational shaft <NUM> on which the thrust acts.

The second housing <NUM> may be referred to as an opposite load-side housing in that it is located on an opposite side of the load-side housing.

The second housing <NUM> may be inserted into the shroud <NUM>.

The second housing <NUM> is disposed at a downstream side of the first housing <NUM> based on the air flow direction.

The second housing <NUM> includes a second coupling ring <NUM>, an accommodating portion <NUM>, a second bearing housing 152b, and a second bridge <NUM>.

The second coupling ring <NUM> is formed in a circular ring shape. The second coupling ring <NUM> is disposed to face the first coupling ring <NUM>.

An outer diameter of the second coupling ring <NUM> is formed to correspond to an inner diameter of the coupling portion <NUM> of the shroud <NUM>. The second coupling ring <NUM> may be press-fitted to an inner circumferential surface of the coupling portion <NUM> of the shroud <NUM>.

The first coupling ring <NUM> and the second coupling ring <NUM> may have different radial widths. For example, the radial width of the second coupling ring <NUM> may be larger than the radial width of the first coupling ring <NUM>.

The radial width of the second coupling ring <NUM> may be larger than or equal to the radial width of the another axial end of the flow guide <NUM>. The radial width of the second coupling ring <NUM> is formed to be constant along the axial direction.

An inner rim of the one axial end of the second coupling ring <NUM> is formed in a curved shape. This can minimize flow resistance of air that flows into the second coupling ring <NUM> from the flow guide <NUM>.

The second coupling ring <NUM> defines an accommodation space therein to accommodate a stator core <NUM> of the motor unit, which will be described later.

A protrusion rib <NUM> protrudes from the another end of the first bridge <NUM> into the inner accommodation space of the second coupling ring <NUM>. The protrusion rib <NUM> may protrude in a direction opposite to the first coupling ring <NUM>. An outer circumferential surface of the protrusion rib <NUM> is formed to be in surface contact with an inner circumferential surface of the second coupling ring <NUM>.

A coupling hole <NUM> is formed through an outer end portion of each of the first bridge <NUM> in the axial direction. A diameter of the coupling hole <NUM> is smaller than a circumferential width of the first bridge <NUM>.

The coupling hole <NUM> is disposed between the first coupling ring <NUM> and the protrusion rib <NUM>. The coupling hole <NUM> is provided in plurality disposed spaced apart from one another at equal intervals along the circumferential direction of the flow guide <NUM>. This embodiment illustrates that the plurality of coupling holes <NUM> are spaced apart at <NUM>-degree intervals.

With this configuration, the protrusion rib <NUM> can reinforce strength of the first bridge <NUM> that is reduced due to the coupling hole <NUM>. In addition, the protrusion rib <NUM> may protrude to be fitted into the inner circumferential surface of the second coupling ring <NUM> so as to improve an assembling property between the first housing <NUM> and the second housing <NUM>.

A plurality of second fastening grooves <NUM> may be formed in the one axial end of the second coupling ring <NUM>. The second fastening groove <NUM> overlaps the coupling hole <NUM> in the axial direction.

The second fastening member <NUM>, such as a screw, is fastened to the first bridge <NUM> and the second coupling ring <NUM> through the coupling hole <NUM> and the second fastening groove <NUM>. Through this, the first housing <NUM> and the second housing <NUM> are fastened to each other by the second fastening member <NUM>.

The second bearing housing 152b is formed in a cylindrical shape. An accommodation space is defined inside the second bearing housing 152b to accommodate the second bearing 151b. The second bearing housing 152b is formed in a penetrating manner in the axial direction. The second bearing housing 152b may surround the second bearing 151b.

The accommodating portion <NUM> is disposed at the downstream side of the second coupling ring <NUM>. The accommodating portion <NUM> is made to accommodate a portion of the motor unit, for example, coils <NUM> of a stator <NUM> to be described later and the second bearing housing 152b.

The accommodating portion <NUM> is formed in a cylindrical shape. An inner diameter of the accommodating portion <NUM> is smaller than a diameter of the second coupling ring <NUM> and larger than a diameter of the second bearing housing 152b.

One axial end of the accommodating portion <NUM> may be connected to another axial end of the second coupling ring <NUM>.

A radial reduction portion <NUM> extends in the radial direction between the another axial end of the second coupling ring <NUM> and the one axial end of the accommodating portion <NUM>. The radial reduction portion <NUM> connects the another axial end of the second coupling ring <NUM> and the one axial end of the accommodating portion <NUM>.

The second bearing housing 152b is disposed inside the accommodating portion <NUM>. The second bearing housing 152b is disposed at a downstream side of the coils <NUM> of the stator <NUM> based on the air flow direction.

The second bridge <NUM> may extend radially between the accommodating portion <NUM> and the second bearing housing 152b. An outer end portion of the second bridge <NUM> may be connected to another axial end of the accommodating portion <NUM>. An inner end portion of the second bridge <NUM> may be connected to an outer circumferential surface of the second bearing housing 152b.

An inner end portion of the second bridge <NUM> may be connected to the another axial end of the second bearing housing 152b. The second bridge <NUM> may be provided in plurality. The plurality of second bridges <NUM> may be spaced apart from one another in the circumferential direction of the second bearing housing 152b.

A plurality of first discharge holes 126a may be formed between the plurality of second bridges <NUM> adjacent to each other in the circumferential direction to allow air to flow to the outside. The plurality of first discharge holes 126a and the plurality of second bridges <NUM> each are alternately arranged in a spaced manner along the circumferential direction.

Accordingly, air passing through the accommodating portion <NUM> can be discharged in the axial direction through the plurality of first discharge holes 126a.

A plurality of second discharge holes 126b may be formed through a side surface of the accommodating portion <NUM> in the radial direction. The plurality of second discharge holes 126b may be spaced apart in the circumferential direction. According to this, air can be discharged radially from the inside of the accommodating portion <NUM>.

The motor unit receives electrical energy to rotate the rotational shaft <NUM> and rotates the impeller <NUM> mounted on one end portion of the rotational shaft <NUM>.

To this end, the motor unit includes a rotor <NUM> and a stator <NUM>.

The rotor <NUM> includes a rotor core <NUM> and a permanent magnet <NUM>.

The rotor core <NUM> may be formed by stacking thin electrical steel sheets in the axial direction. The rotor core <NUM> is formed in a cylindrical shape. A shaft through-hole is formed through a central portion of the rotor core <NUM>. The shaft through-hole is formed through the rotor core <NUM> in the axial direction.

The rotor core <NUM> is mounted on the rotational shaft <NUM>. A rotor support portion is provided on the rotational shaft <NUM>. The rotational shaft <NUM> includes a first bearing support portion and a second bearing support portion. The rotor support portion is disposed between the first bearing support portion and the second bearing support portion. A diameter of the rotor support portion may be larger than diameters of the first bearing support portion and the second bearing support portion.

The rotor <NUM> may be disposed between the first bearing 151a and the second bearing 151b.

The permanent magnet <NUM> may be embedded inside the rotor core <NUM> or mounted on an outer circumferential surface of the rotor core <NUM>. In this embodiment, the permanent magnet <NUM> is shown mounted on the outer circumferential surface of the rotor core <NUM>.

The stator <NUM> includes a stator core <NUM> and coils <NUM>.

The stator core <NUM> may be formed by stacking thin electrical steel sheets in the axial direction. The stator core <NUM> is formed in a cylindrical shape. A rotor through-hole is formed through a central portion of the stator core <NUM>. The rotor through-hole is formed through the stator core <NUM> in the axial direction.

A diameter of the rotor through-hole is slightly larger than the diameter of the permanent magnet <NUM>. The permanent magnet <NUM> may maintain a preset distance (air gap) from an inner circumferential surface of the stator core <NUM>.

The stator core <NUM> includes a back yoke, a plurality of slots, and a plurality of teeth.

The back yoke is formed in a cylindrical shape.

The plurality of teeth are formed to protrude from the back yoke toward the rotational shaft <NUM> in the radial direction. Pole shoes may protrude in the circumferential direction from inner end portions of the plurality of teeth.

The plurality of slots are formed to penetrate through the stator core <NUM> in the axial direction. The plurality of teeth and the plurality of slots each are alternately arranged in a spaced manner in the circumferential direction of the stator core <NUM>. This embodiment illustrates three teeth and three slots.

The plurality of teeth and the plurality of slots each may be spaced apart from one another at intervals of <NUM> degrees in the circumferential direction.

The plurality of coils <NUM> are wound on the stator core <NUM> through the plurality of slots, respectively. In this embodiment, three coils <NUM> are illustrated. Three-phase AC currents may be applied to the three coils <NUM>.

The stator <NUM> is provided with a plurality of connectors <NUM> so that external three-phase AC power is supplied to the coils <NUM>. In this embodiment, three connectors <NUM> are provided one by one for each phase.

The connectors <NUM> are made to electrically connect an external three-phase AC power source and the coils <NUM>. The connectors <NUM> extend downward from the stator core <NUM> in the axial direction.

A plurality of lead wires <NUM> protrude from a lower side of the connector <NUM> in the axial direction to be exposed to the outside.

Connector accommodating holes are formed in the accommodating portion <NUM> to accommodate the connectors <NUM>, respectively.

Insulators <NUM> are provided for electrical insulation between the coils <NUM> and the stator core <NUM>. The insulators <NUM> may be made of a non-conductor.

The insulators <NUM> may be disposed between the coils <NUM> and the stator core <NUM> to block current from flowing between the coils <NUM> and the stator core <NUM>.

The plurality of coils <NUM> and the plurality of insulators <NUM> each may be spaced apart from one another at intervals of <NUM> degrees along the circumferential direction of the stator core <NUM>.

The first bridges <NUM> are located at the upper side of the motor unit. The first bridges <NUM> and the coils <NUM> (or teeth) may be disposed so as not to overlap each other in the axial direction. The first bridges <NUM> do not hinder the flow of air guided by the flow guide <NUM> from the vanes <NUM>.

The second bridges <NUM> are located at a lower side of the motor unit. The second bridges <NUM> and the coils <NUM> (or teeth) may be disposed to overlap each other in the axial direction.

The first bearing 151a and the second bearing 151b respectively supporting both sides of the rotational shaft <NUM> are supported by the first housing <NUM> and the second housing <NUM> which are different from each other.

Each of the first housing <NUM> and the second housing <NUM> is formed in a cylindrical shape. The first and second housings <NUM> and <NUM> have the same outermost diameter. The first and second housings <NUM> and <NUM> may be press-fitted to the inner circumferential surface of the coupling portion <NUM> of the single shroud <NUM> and may be fastened to each other in the axial direction.

However, the first housing <NUM> and the second housing <NUM> may not be aligned with each other in the axial direction due to various reasons such as molding or assembly tolerance.

Due to this, the first bearing 151a and the second bearing 151b supporting the single rotational shaft <NUM> are minutely misaligned with respect to the longitudinal direction of the shroud <NUM>, which causes concentricity misalignment.

In addition, the rotational shaft <NUM> may be misaligned to be tilted with respect to the longitudinal direction of the shroud <NUM>.

Therefore, in order to solve a problem of wear due to friction between the rotational shaft <NUM> and the bearing <NUM>, which is caused by axial misalignment between the first and second bearings 151a and 151b, a heat dissipation fin <NUM> having a self-aligning function is provided.

The heat dissipation fin <NUM> is disposed between the bearing housing <NUM> and the bearing <NUM>. The heat dissipation fin <NUM> may be applied to only one bearing <NUM> or to both bearings <NUM> in a double-side bearing support structure.

This embodiment illustrates an example in which the heat dissipation fin <NUM> is applied to only one of the both bearings <NUM>. In particular, the heat dissipation fin <NUM> is shown disposed between the second bearing housing 152b and the second bearing 151b that are far apart from the impeller <NUM>.

However, when the heat dissipation fins <NUM> are applied to the both bearings <NUM>, the self-aligning function can be further improved.

The heat dissipation fin <NUM> includes an outer ring part <NUM>, an inner ring part <NUM>, and a connection part <NUM>.

The outer ring part <NUM> and the inner ring part <NUM> may extend in the axial direction. The outer ring part <NUM> may be disposed to surround the inner ring part <NUM>. The outer ring part <NUM> may be spaced apart from the inner ring part <NUM> while maintaining a constant distance.

The outer ring part <NUM> may be formed in a cylindrical shape. The outer ring part <NUM> may be disposed to face the second bearing housing 152b in the radial direction.

An outer diameter of the outer ring part <NUM> may correspond to an inner diameter of the second bearing housing 152b. The second bearing housing 152b may cover the outer ring part <NUM> in contact with the outer ring part <NUM>.

The outer ring part <NUM> may be concentrically disposed together with the second bearing housing 152b with respect to the rotational shaft <NUM>. An axial center line passing through a center of the outer ring part <NUM> in the axial direction and an axial center line passing through a center of the second bearing housing 152b in the axial direction may form the same straight line.

An outer circumferential surface of the outer ring part <NUM> may be in parallel to an inner circumferential surface of the second bearing housing 152b.

The inner ring part <NUM> is disposed inside the outer ring part <NUM>. The inner ring part <NUM> may be formed in a cylindrical shape. The inner ring part <NUM> may be disposed to face the second bearing 151b in the radial direction.

An inner diameter of the inner ring part <NUM> may correspond to an outer diameter of the second bearing 151b. The inner ring part <NUM> may surround the second bearing 151b in contact with the second bearing 151b.

The inner ring part <NUM> may be concentrically disposed together with the second bearing 151b with respect to the rotational shaft <NUM>. An axial center line passing through a center of the inner ring part <NUM> in the axial direction and an axial center line passing through a center of the second bearing 151b in the axial direction may form the same straight line.

An inner circumferential surface of the inner ring part <NUM> may be in parallel to an outer circumferential surface of the second bearing 151b.

The second bearing housing 152b and the second bearing 151b may be spaced apart from each other in the radial direction with the heat dissipation fin <NUM> interposed therebetween.

The connection part <NUM> is disposed between the outer ring part <NUM> and the inner ring part <NUM>. The connection part <NUM> connects the outer ring part <NUM> and the inner ring part <NUM>.

The connection part <NUM> extends from the inner circumferential surface of the outer ring part <NUM> to the outer circumferential surface of the inner ring part <NUM>. The connection part <NUM> extends in the radial direction between the outer ring part <NUM> and the inner ring part <NUM>. The connection part <NUM> may extend in the circumferential direction between the inner circumferential surface of the outer ring part <NUM> and the outer circumferential surface of the inner ring part <NUM>.

The connection part <NUM> may be provided in one in the circumferential direction or provided in plurality to be spaced apart from each other in the circumferential direction. This embodiment illustrates an example of employing the single connection part continuously extending along the circumferential direction.

A radially outer end portion of the connection part <NUM> may be connected to the outer ring part <NUM>, and a radially inner end portion of the connection part <NUM> may be connected to the inner ring part <NUM>.

The outer ring part <NUM> and the inner ring part <NUM> may extend to have the same axial length. However, with no limit to this, the axial lengths of the outer ring part <NUM> and the inner ring part <NUM> may be different from each other.

The connection part <NUM> may be connected to axial central portions of the outer ring part <NUM> and the inner ring part <NUM>.

The outer ring part <NUM> and the inner ring part <NUM> may be formed symmetrically in the axial direction, with respect to the connection part <NUM>.

Both axial end portions <NUM> and <NUM> of the inner ring part <NUM> are free ends on the connection part <NUM>.

Here, the free end means one axial end portion <NUM> or another axial end portion <NUM> of the inner ring part <NUM> that is freely movable in the radial direction relative to one side of the inner ring part <NUM> supported by the connection part <NUM>.

One end portion <NUM> of the outer ring part <NUM> and the one end portion <NUM> of the inner ring part <NUM> are spaced apart from each other radially to be open in the second axial direction (the direction that thrust acts), and another end portion <NUM> of the outer ring part <NUM> and the another end portion <NUM> of the inner ring part <NUM> are spaced apart from each other radially to be open in the first axial direction (the direction that air is suctioned).

The connection part <NUM> may elastically support the both axial end portions <NUM> and <NUM> of the outer ring part <NUM> and the both axial end portions <NUM> and <NUM> of the inner ring part <NUM>.

However, the outer ring part <NUM> may be supported in contact with the inner circumferential surface of the second bearing housing 152b.

Both of the axial end portions <NUM> and <NUM> of the inner ring part <NUM> may be elastically deformed by an external force around the connection part <NUM>.

For example, the both axial end portions <NUM> and <NUM> of the inner ring part <NUM> may be elastically deformed according to an inclined arrangement of the rotational shaft <NUM>. The inner ring part <NUM> may be elastically deformed in a direction parallel to an inclination direction of the rotational shaft <NUM> with respect to the outer ring part <NUM>.

According to this configuration, even if the axial alignment between the first bearing 151a and the second bearing 151b is not made, the inner ring part <NUM> surrounding the second bearing 151b can be elastically deformed in the direction parallel to the inclination direction of the rotational shaft <NUM>, which may result in minimizing an occurrence of wear due to friction between the rotational shaft <NUM> and the second bearing 151b.

The heat dissipation fin <NUM> further includes a protrusion <NUM>.

The protrusion <NUM> protrudes radially from the another axial end portion of the inner ring part <NUM> toward the rotational shaft <NUM>. The protrusion <NUM> may be formed in a circular ring shape. The protrusion <NUM> may extend along the circumferential direction of the inner ring part <NUM> while maintaining the same width.

An inner diameter of the protrusion <NUM> may be larger than or equal to the diameter of the rotational shaft <NUM>.

A wave washer <NUM> may be disposed between the another axial end portion of the second bearing 151b and the protrusion <NUM>. The wave washer <NUM> may be formed in a wavy ring shape. The wave washer <NUM> may be formed of a metal material having elasticity.

An outer diameter of the wave washer <NUM> may be smaller than or equal to that of the inner ring part <NUM>. An inner diameter of the wave washer <NUM> may be larger than or equal to that of the rotational shaft <NUM>. A diameter of the wave washer <NUM> may correspond to that of the second bearing 151b.

The wave washer <NUM> applies a preload to the inner ring of the bearing <NUM> in the axial direction, thereby minimizing radial or axial vibration of the balls of the ball bearing between the outer ring and the inner ring.

The protrusion <NUM> may prevent the wave washer <NUM> from being axially separated from the inside of the inner ring part <NUM>.

The heat dissipation fin <NUM> may perform a heat dissipation function to dissipate heat, which is generated from the rotational shaft <NUM> and the bearing <NUM> during fast rotation of the fan motor, to the outside.

To this end, the heat dissipation fin <NUM> is formed of a metal material having a high heat transfer coefficient.

In addition, the heat dissipation fin <NUM> further includes a plurality of heat dissipation expansion ribs <NUM>.

The heat dissipation expansion ribs <NUM> may be provided on the outer ring part <NUM>. The heat dissipation extension rib <NUM> may extend radially outward from an outer circumferential portion of the outer ring part <NUM>. The heat dissipation expansion ribs <NUM> are formed in a plate shape.

The heat dissipation expansion ribs <NUM> may be formed in a rectangular shape with a length longer than a width. The heat dissipation expansion ribs <NUM> may be formed to correspond to the second bridges <NUM>. The second bridges <NUM> may be formed in a rectangular plate shape.

The heat dissipation expansion ribs <NUM> may be supported by the outer ring part <NUM>. However, a lower surface of the heat dissipation expansion rib <NUM> may be stacked on an upper surface of the second bridge <NUM>.

The plurality of heat dissipation expansion ribs <NUM> may be spaced apart from one another in the circumferential direction. The plurality of heat dissipation expansion ribs <NUM> may be arranged to overlap the coils <NUM> in the axial direction. The heat dissipation expansion ribs <NUM> may be spaced apart from the coils <NUM> at preset intervals in the axial direction. In this embodiment, three heat dissipation expansion ribs <NUM> are provided to be spaced apart at intervals of <NUM> degree in the circumferential direction.

According to this, the heat dissipation expansion ribs <NUM> can increase a contact area with air, such that heat transferred from the outer ring part <NUM> can be dissipated into air that is flowing inside the accommodating portion <NUM>.

The heat dissipation expansion ribs <NUM> extend on the upper surfaces of the second bridges <NUM> and are connected to the second housing <NUM> through the second bridges <NUM>, thereby increasing support strength of the heat dissipation fins <NUM>.

In addition, the heat dissipation expansion ribs <NUM> are arranged to overlap the coils <NUM> so as not to interfere with the flow of air that is flowing axially in a space between the plurality of coils <NUM>, thereby minimizing flow resistance of air that is discharged through the first discharge holes 126a between the plurality of second bridges <NUM>.

The heat dissipation fins <NUM> are disposed at a downstream side of the coils <NUM> based on an air flow direction.

Since the heat dissipation fin <NUM> is a metal conductor, current flowing through the coil <NUM> may flow to the heat dissipation fin <NUM> if a distance between the coil <NUM> and the heat dissipation fin <NUM> is short. In order to prevent such current flowing through the coil <NUM> from leaking to the heat dissipation fin <NUM>, an insulation distance must be secured between the coil <NUM> and the heat dissipation fin <NUM>.

However, if an axial distance between the coil <NUM> and the second bearing 151b is increased to secure the insulation distance between the coil <NUM> and the heat dissipation fin <NUM>, the rotational shaft <NUM> elongates and thereby an axial length of the fan motor increases, which causes a problem of enlarging the fan motor.

Therefore, it is necessary to shorten the axial length of the fan motor while securing the insulation distance between the coil <NUM> and the heat dissipation fin <NUM>.

To this end, an insulation cover <NUM> may be provided between the coil <NUM> and the heat dissipation fin <NUM>. The insulation cover <NUM> may be formed of a plastic material.

The insulation cover <NUM> is provided to cover one axial end of the heat dissipation fin <NUM>. The insulation cover <NUM> may extend radially inward from one axial end of the second bearing housing 152b toward the rotational shaft <NUM>.

An inner end portion of the insulation cover <NUM> may be spaced apart from the rotational shaft <NUM> at a preset distance (air gap).

The insulation cover <NUM> may be formed to cover one axial end and an outer circumferential surface of the second bearing housing 152b.

The insulation cover <NUM> may be provided in plurality. The plurality of insulation covers <NUM> may be spaced apart from one another at preset intervals in the circumferential direction of the second bearing housing 152b. The insulation covers <NUM> may be supported by being connected to the accommodating portion <NUM> of the second housing <NUM>.

A distance between the coil <NUM> and the outer ring part <NUM> (or the inner ring part <NUM>) is shorter than a distance between the coil <NUM> and the heat dissipation expansion rib <NUM>.

The insulation cover <NUM> is disposed between the coil <NUM> and the outer ring part <NUM> (or the inner ring part <NUM>). The insulation cover <NUM> covers the outer ring part <NUM> and the inner ring part <NUM>.

According to this, the insulation cover <NUM> disposed between the coil <NUM> and the heat dissipation fin <NUM> can block current from flowing between the coil <NUM> and the heat dissipation fin <NUM>.

Hereinafter, operations and effects of a fan motor according to one embodiment of the present disclosure will be described.

An operating state of the fan motor will first be described as follows.

When current is applied to the coil <NUM> of the stator <NUM> through the lead wire <NUM>, a magnetic field is generated around the coil <NUM>. The coil <NUM> of the stator <NUM> and the permanent magnet <NUM> of the rotor <NUM> interact electromagnetically with each other, so that the rotor <NUM> rotates relative to the stator <NUM> centering on the rotational shaft <NUM>. The rotational shaft <NUM> rotates together with the rotor <NUM> and transmits rotational force to the impeller <NUM>. The impeller <NUM> is rotated by the rotational force transmitted through the rotational shaft <NUM>.

The impeller <NUM> rotates air and suctions external air into the shroud <NUM> through the inlet port <NUM>. The suctioned air passes through the vanes <NUM>. The vanes <NUM> switch a rotational flow of the air to an axial flow.

The air which has been switched to the axial flow is guided by the flow guide <NUM> and moves toward the motor unit from the inside of the first coupling ring <NUM> of the first housing <NUM>. The air comes into contact with the stator core <NUM> and the coil <NUM> of the motor unit, so as to cool heat generated from the coil <NUM>.

After cooling the coil <NUM>, the air passes through the motor unit and is discharged to the outside through the first discharge holes 126a between the second bridges <NUM> and the second discharge holes 126b formed through the side surface of the accommodating portion <NUM>.

The plurality of bearings <NUM> rotatably support the rotational shaft <NUM>.

The first bearing 151a and the second bearing 151b can stably support both sides of the rotational shaft <NUM> with the relatively heavy rotor <NUM> interposed therebetween.

In order to reduce a weight of a fan motor of a cleaner, a material of a casing and the like may change to a plastic material instead of a metal. Here, components whose material can be changed to the plastic material, may include not only the shroud <NUM> of the casing and the first and second housings <NUM> and <NUM>, but also the impeller <NUM>, the bearing housing <NUM>, the stopper <NUM>, the insulation cover <NUM>, and the like.

However, since the plastic material has a lower heat transfer coefficient than the metal material, a temperature of the bearing <NUM> or the like increases. This may shorten a lifespan of the bearing <NUM> and deteriorate reliability of the fan motor.

In order to solve these problems, the heat dissipation fin <NUM> that is made of a metal material having a shape exposed to air while enclosing the bearing <NUM> and having a high heat transfer coefficient is provided.

The heat dissipation fin <NUM> made of the metal material may be integrally molded with the bearing housing <NUM> by insert-injection when the bearing housing <NUM> is manufactured. During plastic injection for manufacturing the bearing housing <NUM>, the heat dissipation fin <NUM> made of the metal material may be inserted into a mold and thereafter manufactured integrally with the bearing housing made of a different material.

However, when the heat dissipation fin <NUM> is manufactured by insert injection into the bearing housing <NUM> made of the plastic material, it is difficult to offer correct alignment of the heat dissipation fin <NUM>. This may cause an alignment problem between the bearings <NUM> during the operation of the fan motor.

Therefore, the present disclosure provides the heat dissipation fin <NUM> having the shape that is capable of securing (aligning, maintaining) concentricity between the bearings <NUM> while reducing temperatures of the bearings <NUM>.

<FIG> is a conceptual view illustrating a self-aligning function of the heat dissipation fin <NUM> in <FIG>.

The heat dissipation fin <NUM> of the present disclosure encloses the bearing <NUM>. For example, the heat dissipation fin <NUM> may have a cross-section formed in an "H" shape or in a "∩" or " ∪" shape. In this embodiment, the heat dissipation fin <NUM> has the cross-section in the "H" shape.

In order to maximize an area exposed to air, the outer ring part <NUM> and the inner ring part <NUM> of the heat dissipation fin <NUM> are spaced apart from each other in a direction perpendicular to the rotational shaft <NUM>.

Through this, air can be introduced through an opening between the outer ring part <NUM> and the inner ring part <NUM>, to be brought into contact with the inner circumferential surface of the outer ring part <NUM> and the outer circumferential surface of the inner ring part <NUM>. This can enlarge a contact area between the air and the heat dissipation fin <NUM>.

In addition, the inner circumferential surface of the inner ring part <NUM> may come into contact with the bearing <NUM> to transfer heat to the connection part <NUM> and the outer ring part <NUM>.

The air can also be brought into contact with the connection part <NUM>, by which the outer ring part <NUM> and the inner ring part <NUM> are connected to each other, so as to increase the contact area between the air and the heat dissipation fin <NUM>. This can improve a heat dissipation performance of the heat dissipation fin <NUM>.

The plurality of heat dissipation expansion ribs <NUM> may extend radially outward from the outer ring part <NUM> of the heat dissipation fin <NUM> and have a thin thickness and a large area, so that the contact area between the air and the heat dissipation fin <NUM> can be expanded.

The plurality of heat dissipation expansion ribs <NUM> may be arranged to overlap the coils <NUM> in the axial direction. According to this, the heat dissipation expansion ribs <NUM> can maximize an area, by which the heat dissipation fin <NUM> is exposed to the air, while minimizing flow resistance when the air passed through the coils <NUM> is discharged.

The first bearing 151a may be disposed adjacent to the impeller <NUM>, and the hub <NUM> of the impeller <NUM> may cover the first bearing 151a. Air suctioned by the impeller <NUM> does not flow to the first bearing 151a but moves toward the second bearing 151b.

The opening between the outer ring part <NUM> and the inner ring part <NUM> of the heat dissipation fin <NUM> can face a moving direction of the air suctioned by the impeller <NUM>. Accordingly, heat generated from the bearing <NUM> can be efficiently dissipated. It is more effective in reducing a temperature of the bearing <NUM>.

The first bearing 151a supported by the first bearing housing 152a and the second bearing 151b supported by the second bearing housing 152b may not be axially aligned with each other.

For example, when the second bearing 151b is disposed eccentrically to one side with respect to the first bearing 151a, the first bearing 151a and the second bearing 151b are arranged to be inclined with respect to a perpendicular line because the first bearing 151a and the second bearing 151b are connected by the rotational shaft <NUM>.

The second bearing 151b is inclined with respect to the perpendicular line. One axial end of the second bearing 151b presses the one axial end <NUM> of the inner ring part <NUM> of the heat dissipation fin <NUM> to the left toward the outer ring part <NUM>. Another axial end of the second bearing 151b presses the another axial end portion <NUM> of the inner ring part <NUM> of the heat dissipation fin <NUM> to the right toward the outer ring part <NUM>.

The one axial end <NUM> and the another axial end <NUM> of the inner ring part <NUM> are elastically deformed along the inclination direction of the rotational shaft <NUM> based on the connection part <NUM>. The outer ring part <NUM> may not be elastically deformed because of being supported by the second bearing housing 152b.

Therefore, according to the present disclosure, the casing and the bearing housing <NUM> are made of a plastic material to reduce the weight of the fan motor of the cleaner. The heat dissipation fin <NUM> that is made of a metal material having a high heat transfer coefficient is inserted into a mold to enclose the bearing <NUM> during plastic injection, and is integrally formed with the bearing housing <NUM> made of the plastic material through insert-injection.

The both axial end portions <NUM> and <NUM> of the inner ring part <NUM> of the heat dissipation fin <NUM> that encloses the bearing <NUM> are free ends that are bent in the radial direction around the connection part <NUM>, and are elastically supported by the connection part <NUM>.

With this configuration, even when the concentricity and the axial alignment are not obtained between the first bearing 151a and the second bearing 151b supporting the both ends of the rotational shaft <NUM>, the inner ring part <NUM> of the heat dissipation fin <NUM> can be elastically deformed to be inclined in the direction in parallel to the rotational shaft <NUM> according to the inclination of the rotational shaft <NUM> while enclosing the bearing <NUM>, thereby improving the axial alignment between the bearings <NUM>.

<FIG> is a sectional view illustrating a fan motor in accordance with another embodiment.

<FIG> is a perspective view illustrating a structure of a heat dissipation fin <NUM> in <FIG>.

<FIG> is a planar view illustrating the heat dissipation fin <NUM> of <FIG>, viewed from a top.

<FIG> is a sectional view illustrating the heat dissipation fin <NUM>, taken along a line XIII-XIII in <FIG>.

This embodiment is different from the embodiment of <FIG> in view of a cross-sectional shape of the heat dissipation fin <NUM>.

The heat dissipation fin <NUM> is formed to enclose the second bearing 151b. The heat dissipation fin <NUM> is disposed between the second bearing housing 152b and the second bearing 151b.

The heat dissipation fin <NUM> includes an outer ring part <NUM>, an inner ring part <NUM>, a connection part <NUM>, a protrusion <NUM>, and a plurality of heat dissipation expansion ribs <NUM>.

The outer ring part <NUM> is formed in a cylindrical shape with a first diameter. The outer ring part <NUM> has a first hollow hole inside.

The inner ring part <NUM> is formed in a cylindrical shape with a second diameter. The first diameter is larger than the second diameter. The inner ring part <NUM> has a second hollow hole inside. A diameter of the first hollow hole is larger than that of the second hollow hole.

The outer ring part <NUM> is formed to surround the inner ring part <NUM>. The inner ring part <NUM> is disposed inside the outer ring part <NUM>. The outer ring part <NUM> and the inner ring part <NUM> are concentrically arranged to have the same center.

An outer circumferential surface of the outer ring part <NUM> may be coupled to be in surface-contact with the inner circumferential surface of the second bearing housing 152b.

An inner circumferential surface of the inner ring part <NUM> may be coupled to be in surface-contact with the outer circumferential surface of the second bearing 151b.

The outer ring part <NUM> and the inner ring part <NUM> may extend to have the same axial length.

The connection part <NUM> extends from one axial end <NUM> of the outer ring part <NUM> to one axial end <NUM> of the inner ring part <NUM>. The connection part <NUM> may extend in the radial direction. The connection part <NUM> may be disposed at an upstream side of the outer ring part <NUM> and the inner ring part <NUM> based on an air flow direction.

The protrusion <NUM> protrudes from another axial end <NUM> of the inner ring part <NUM> toward the rotational shaft <NUM>. The protrusion <NUM> may extend radially inward. The protrusion <NUM> covers the another axial end of the second bearing 151b.

The protrusion <NUM> may be disposed at a downstream side of the inner ring part <NUM> based on the air flow direction. The protrusion <NUM> and the connection part <NUM> may be disposed on both ends of the inner ring part <NUM> at opposite sides to each other.

The one axial end <NUM> of the inner ring part <NUM> may be supported by being connected to the connection part <NUM>.

The another axial end <NUM> of the inner ring part <NUM> is spaced apart from the outer ring part <NUM> in the radial direction and is a free end.

The another axial end <NUM> of the inner ring part <NUM> and the protrusion <NUM> may be elastically deformed toward the outer ring part <NUM> based on the connection part <NUM> when an external force is applied in the radial direction.

The heat dissipation expansion rib <NUM> protrudes radially outward from the outer ring part <NUM> toward the another axial end of the accommodating portion <NUM> through the another axial end of the second bearing housing 152b. The plurality of heat dissipation expansion ribs <NUM> may be disposed on the outer ring part <NUM> to be spaced apart from one another at preset intervals along the circumferential direction.

In this embodiment, the heat dissipation expansion ribs <NUM> are spaced apart at intervals of <NUM> degrees in the circumferential direction. The heat dissipation extension ribs <NUM> may be formed up to the inner circumferential surface of the accommodating portion <NUM> or may extend up to the middle of the second bridges <NUM>.

This embodiment illustrates an example in which the heat dissipation expansion ribs <NUM> extend up to the middle of the second bridges <NUM>.

The second bearing housing 152b made of the plastic material and the heat dissipation fin <NUM> made of the metal material may be integrally formed with each other through insert-injection.

Therefore, according to this embodiment, the heat dissipation fin <NUM> can be formed of a metal material having a high heat transfer coefficient while enclosing the bearing <NUM>, and the inclination of the bearing <NUM> can be automatically adjusted in the direction in parallel to the rotational shaft <NUM> when the axial alignment between the bearings <NUM> is not secured, thereby improving concentricity and alignment between the bearings <NUM>.

Since other components are the same as or similar to those of <FIG> described above, duplicate descriptions will be omitted.

<FIG> is an exploded view illustrating components of a fan motor in accordance with still another embodiment of the present disclosure.

<FIG> is a sectional view illustrating a state in which the components of the fan motor of <FIG> are coupled.

<FIG> is a conceptual view illustrating a self-aligning function of heat dissipation fins 160a and 160b in <FIG>.

This embodiment is different from the previous embodiment of <FIG> in that a plurality of heat dissipation fins 160a and 160b are provided to enclose the first bearing 151a and the second bearing 151b, respectively.

The plurality of heat dissipation fins 160a and 160b include a first heat dissipation fin 160a and a second heat dissipation fin 160b. The first heat dissipation fin 160a may be accommodated inside the first bearing housing 152a while enclosing the first bearing 151a.

This embodiment is the same as or similar to the previous embodiment of <FIG> in that each of the first heat dissipation fin 160a and the second heat dissipation fin 160b includes an outer ring part 161a, 161b, an inner ring part 162a, 162b, a connection part 163a, 163b, a protrusion 165a, 165b, and heat dissipation expansion ribs 164a, 164b.

However, structure and arrangement direction of the first heat dissipation fin 160a is different from structure and arrangement direction of the second heat dissipation fin 160b in view of the following points.

The protrusion 165a of the first heat dissipation fin 160a protrudes radially inward from one axial end of the inner ring part 162a. Here, the one axial end of the inner ring part 162a means an upstream side of the inner ring part 162a based on an air flow direction.

The protrusion 165a of the first heat dissipation fin 160a faces a stopper <NUM>. The stopper <NUM> covers the protrusion 165a and the first bearing 151a.

The inner ring part 162a of the first heat dissipation fin 160a may define an opening that is open toward a downstream side based on the air flow direction. The first bearing 151a is accommodated inside the inner ring part 162a through the opening.

The heat dissipation expansion ribs 164a of the first heat dissipation fin 160a are located between one axial end <NUM> and another axial end <NUM> of the outer ring part 161a. That is, the heat dissipation expansion ribs 164a of the first heat dissipation fin 160a may not be disposed on the one axial end <NUM> or the another axial end <NUM> of the outer ring part 161a, but may be disposed close to the connection part 163a in the axial direction.

The heat dissipation expansion ribs 164a are provided on an outer circumferential surface of the outer ring part 161a, and the connection part 163a is provided on an inner circumferential surface of the outer ring part 161a.

Rib mounting grooves for mounting the heat dissipation expansion ribs 164a are formed in the one axial ends of the first bridges <NUM>. The heat dissipation expansion ribs 164a may be mounted in the rib mounting grooves to face the vane hub <NUM>. The heat dissipation expansion ribs 164a may be disposed between the vane hub <NUM> and the first bridges <NUM>.

The heat dissipation expansion rib 164a may be shorter than a radial length of the first bridge <NUM>.

Third fastening holes 164a1 may be formed through the heat dissipation expansion ribs 164a in the axial direction, respectively. The third fastening hole 164a1 may be disposed to overlap the second fastening hole <NUM> of the vane hub <NUM> and the first fastening groove <NUM> of the first bridge <NUM> in the axial direction. The first fastening member <NUM> such as a screw can be fastened to the first fastening groove <NUM> of the first bridge <NUM> sequentially through the first fastening hole <NUM> of the vane cover <NUM>, the second fastening hole <NUM> of the vane hub <NUM>, and the third fastening hole 164a1 of the heat radiation expansion rib 164a.

The heat dissipation expansion ribs 164a are disposed between the vane hub <NUM> and the first bridges <NUM>, respectively, and fastened to the vane hub <NUM> and the first bridges <NUM> by the first fastening members <NUM>. This can further increase support strength of the heat dissipation fin 160a, 160b.

According to this embodiment, the first heat dissipation fin 160a is further provided to enclose the first bearing 151a. As the first and second heat dissipation fins 160a and 160b enclose the first bearing 151a and the second bearing 151b which support the both sides of the rotational shaft <NUM>, concentricity and alignment between the both bearings <NUM> can be more stably improved. This can minimize an occurrence of wear due to friction between the rotational shaft <NUM> and the bearings <NUM> and also enhance reliability by virtue of the stable support for the bearings <NUM>.

Since other components are the same as or similar to those in the previous embodiment of <FIG>, duplicated descriptions will be omitted.

This embodiment is different from the previous embodiment of <FIG> in that a plurality of heat dissipation fins 260a and 260b are provided to enclose the first bearing 151a and the second bearing 151b, respectively.

The plurality of heat dissipation fins 260a and 260b include a first heat dissipation fin 260a and a second heat dissipation fin 260b. The first heat dissipation fin 260a may be accommodated inside the first bearing housing 152a while enclosing the first bearing 151a.

This embodiment is the same as or similar to the previous embodiment of <FIG> in that each of the first heat dissipation fin 260a and the second heat dissipation fin 260b includes an outer ring part 261a, 261b, an inner ring part 262a, 262b, a connection part 263a, 263b, a protrusion 265a, 265b, and heat dissipation expansion ribs 264a, 264b.

However, structure and arrangement direction of the first heat dissipation fin 260a is different from structure and arrangement direction of the second heat dissipation fin 260b in view of the following points.

The connection part 263a of the first heat dissipation fin 260a may extend in the radial direction between another axial end of the outer ring part 261a and another axial end of the inner ring part 262a. Here, the another axial ends of the outer ring part 261a and the inner ring part 262a mean a downstream side of the outer ring part 261a and the inner ring part 262a based on an air flow direction.

The protrusion 265a of the first heat dissipating fin 260a protrudes radially inward from one axial end of the inner ring part 262a. Here, the one axial end of the inner ring part 262a means an upstream side of the inner ring part 262a based on an air flow direction.

The protrusion 265a of the first heat dissipation fin 260a faces a stopper <NUM>. The stopper <NUM> covers the protrusion 265a and the first bearing 151a.

The connection part 263a and the protrusion 265a of the first heat dissipation fin 260a may be disposed on opposite sides to each other in the axial direction with respect to the inner ring part 262a. The connection part 263a and the protrusion 265a of the first heat dissipation fin 260a may alternatively be disposed on opposite sides to each other in the radial direction with respect to the inner ring part 262a.

The inner ring part 262a of the first heat dissipation fin 260a may define an opening that is open toward a downstream side based on the air flow direction. The first bearing 151a is accommodated inside the inner ring part 262a through the opening.

The heat dissipation expansion ribs 264a of the first heat dissipation fin 260a are located between one axial end and another axial end of the outer ring part 261a. That is, the heat dissipation expansion ribs 264a of the first heat dissipation fin 260a may not be disposed on the one axial end or the another axial end of the outer ring part 261a, but may be disposed on the middle of the outer ring part 261a in the axial direction.

The heat dissipation expansion ribs 264a are provided on an outer circumferential surface of the outer ring part 261a, and the connection part 263a is provided on an inner circumferential surface of the outer ring part 261a.

Rib mounting grooves for mounting the heat dissipation expansion ribs 264a are formed in the one axial ends of the first bridges <NUM>. The heat dissipation expansion ribs 264a may be mounted in the rib mounting grooves to face the vane hub <NUM>. The heat dissipation expansion ribs 264a may be disposed between the vane hub <NUM> and the first bridges <NUM>.

The heat dissipation expansion rib 264a may be shorter than a radial length of the first bridge <NUM>.

Third fastening holes 264a1 may be formed through the heat dissipation expansion ribs 264a in the axial direction, respectively. The third fastening hole 264a1 may be disposed to overlap the second fastening hole <NUM> of the vane hub <NUM> and the first fastening groove <NUM> of the first bridge <NUM> in the axial direction. The first fastening member <NUM> such as a screw can be fastened to the first fastening groove <NUM> of the first bridge <NUM> sequentially through the first fastening hole <NUM> of the vane cover <NUM>, the second fastening hole <NUM> of the vane hub <NUM>, and the third fastening hole 264a1 of the heat radiation expansion rib 264a.

The heat dissipation expansion ribs 264a are disposed between the vane hub <NUM> and the first bridges <NUM>, respectively, and fastened to the vane hub <NUM> and the first bridges <NUM> by the first fastening members <NUM>. This can further increase support strength of the heat dissipation fin 260a, 260b.

According to this embodiment, the first heat dissipation fin 260a is further provided to enclose the first bearing 151a. As the first and second heat dissipation fins 260a and 260b enclose the first bearing 151a and the second bearing 151b which support the both sides of the rotational shaft <NUM>, concentricity and alignment between the both bearings <NUM> can be more stably improved.

In addition, this can minimize an occurrence of wear due to friction between the rotational shaft <NUM> and the bearings <NUM> and also enhance reliability by virtue of the stable support for the bearings <NUM>.

Since other components are the same as or similar to those in the previous embodiment of <FIG>, a duplicated descriptions will be omitted.

<FIG> is a conceptual view illustrating another embodiment of a heat dissipation fin <NUM> in accordance with the present disclosure.

The embodiment is different from the previous embodiments of <FIG> in that the heat dissipation fin <NUM> includes an elastic member <NUM> disposed between the outer ring part <NUM> and the inner ring part <NUM>.

The heat dissipation fin <NUM> is the same as or similar to the previous embodiments of <FIG> in view of including the outer ring part <NUM>, the inner ring part <NUM>, the protrusion <NUM>, and the plurality of heat dissipation expansion ribs <NUM>, and thus duplicate descriptions will be omitted.

The outer ring part <NUM> surrounds and supports the elastic member <NUM>. The inner ring part <NUM> encloses the bearing <NUM>.

The elastic member <NUM> is disposed between the outer ring part <NUM> and the inner ring part <NUM>, and replaces the connection part <NUM>, <NUM>, 263a, and 263b according to the embodiments of <FIG>, so as to perform the self-aligning function of the heat dissipation fin <NUM>.

One axial end or another axial end of the elastic member <NUM> may be coupled to one axial end or another axial end of the outer ring part <NUM>. The elastic member <NUM> may be formed in a cylindrical shape. The elastic member <NUM> includes a linear portion <NUM> and a curved portion <NUM>. The linear portion <NUM> and the curved portion <NUM> may be alternately disposed along the axial direction of the elastic member <NUM>.

The linear portion <NUM> may extend in the circumferential direction. The linear portion <NUM> may be formed in a circular ring shape. The linear portion <NUM> may be disposed to be in surface-contact with the inner circumferential surface of the outer ring part <NUM>. The linear portion <NUM> may be coupled to the outer ring part <NUM>.

The curved portion <NUM> may extend in the circumferential direction. The curved portion <NUM> may be formed in a circular ring shape. The curved portion <NUM> may be convexly formed from the outer ring part <NUM> toward the inner ring part <NUM>. The curved portion <NUM> may be formed in an arcuate shape with a preset curvature.

The curved portion <NUM> may be disposed to be in surface-contact with the outer circumferential surface of the inner ring part <NUM>.

Each of the linear portion <NUM> and the curved portion <NUM> may be provided in one or plurality. This embodiment illustrates that each of the linear portion <NUM> and curved portion <NUM> are provided in plurality.

The linear portion <NUM> and the curved portion <NUM> are integrally formed with each other. The linear portion <NUM> may extend in the axial direction to connect the plurality of curved portions <NUM> adjacent to each other in the axial direction of the heat dissipation fin <NUM>.

The elastic member <NUM> may be formed of a metal material having a high heat transfer coefficient.

According to this configuration, the elastic member <NUM> is disposed between the outer ring part <NUM> and the inner ring part <NUM>. When axial alignment and concentricity between the plurality of bearings <NUM> are not secured, the elastic member <NUM> is elastically deformed according to the inclination of the rotational shaft <NUM>. The inner ring part <NUM> may be elastically supported by the elastic member <NUM> and thus can be radially moved or elastically deformed to be in parallel to the inclination of the rotational shaft <NUM>.

Therefore, the inner ring part <NUM> of the heat dissipation fin <NUM> can be elastically deformed in a direction parallel to the rotational shaft <NUM> while enclosing the bearings <NUM> even when the axial concentricity between the bearings <NUM> is not offered. This can improve the axial alignment and concentricity between the bearings <NUM>.

The heat dissipation fin <NUM> according to this embodiment may be applied to enclose one or both of the bearings <NUM>, namely, the first bearing 151a and the second bearing 151b.

Since other components are the same as or similar to those in the previous embodiments of <FIG>, duplicated descriptions will be omitted.

<FIG> is a conceptual view illustrating still another embodiment of a heat dissipation fin <NUM> in accordance with the present disclosure.

One axial end or another axial end of the elastic member <NUM> may be coupled to one axial end or another axial end of the outer ring part <NUM>. The elastic member <NUM> may be formed in a cylindrical shape. The elastic member <NUM> includes a first curved portion <NUM> and a second curved portion <NUM>. The first curved portion <NUM> and the second curved portion <NUM> may be alternately disposed along the axial direction of the elastic member <NUM>.

The first curved portion <NUM> may extend in the circumferential direction. The first curved portion <NUM> may be formed in a circular ring shape. The first curved portion <NUM> may be convexly formed from the inner ring part <NUM> toward the outer ring part <NUM>.

The first curved portion <NUM> may be formed in an arcuate shape with a preset curvature. The first curved portion <NUM> may be disposed to be in contact with the inner circumferential surface of the outer ring part <NUM>.

The second curved portion <NUM> may extend in the circumferential direction. The second curved portion <NUM> may be formed in a circular ring shape. The second curved portion <NUM> may be convexly formed from the outer ring part <NUM> toward the inner ring part <NUM>.

The second curved portion <NUM> may be formed in an arcuate shape with a preset curvature. The second curved portion <NUM> may be disposed to be in contact with the outer circumferential surface of the inner ring part <NUM>.

Each of the first curved portion <NUM> and the second curved portion <NUM> may be provided in one or plurality. This embodiment illustrates an example in which two first curved portions <NUM> and one first curved portion <NUM> are provided.

The first curved portion <NUM> and the second curved portion <NUM> are integrally formed with each other. The second curved portion <NUM> extends to connect the plurality of first curved portions <NUM> adjacent to each other in the axial direction of the heat dissipation fin <NUM>.

Therefore, the inner ring part <NUM> of the heat dissipation fin <NUM> can be elastically deformed in a direction parallel to the rotational shaft <NUM> while enclosing the bearings <NUM> even when the axial concentricity between the bearings <NUM> is not obtained. This can improve the axial alignment and concentricity between the bearings <NUM>.

Claim 1:
A fan motor comprising:
a rotational shaft (<NUM>) on which an impeller (<NUM>) is mounted;
a plurality of bearings (<NUM>) supporting the rotational shaft (<NUM>);
a plurality of bearing housings (<NUM>) accommodating the plurality of bearings (<NUM>) therein, respectively; and
a heat dissipation fin (<NUM>) enclosing at least one of the plurality of bearings (<NUM>) and mounted on an inner surface of a respective bearing housing (<NUM>),
characterized in that the heat dissipation fin (<NUM>) comprises:
an outer ring part (<NUM>) formed in a cylindrical shape;
an inner ring part (<NUM>) enclosing the at least one of the plurality of bearings (<NUM>), and disposed inside the outer ring part (<NUM>) to be radially spaced apart from an inner circumferential surface of the outer ring part (<NUM>);
a connection part (<NUM>) extending between the outer ring part (<NUM>) and the inner ring part (<NUM>) to connect the outer ring part (<NUM>) and the inner ring part (<NUM>); and
a plurality of heat dissipation expansion ribs (<NUM>) each extending radially outward from an outer circumferential portion of the outer ring part (<NUM>) and spaced apart from one another in a circumferential direction.