Patent Application
20130266463
1. Field of the Invention
The present invention relates to a fan motor including a rotating fan blade.
2. Description of the Related Art
Fan motors that rotate a fan blade are built in electronic devices like a personal computer.
Such fan motors promote heat dissipation inside the electronic device, thereby contributing the downsizing and speedup of such a device.
Fan motors are nowadays often built in especially portable electronic devices like a laptop computer.
In comparison with the fan motors built in stationary electronic devices like a desktop computer, it is necessary for the fan motors built in the portable electronic devices like a laptop computer to have a shock resistance and a vibration resistance in order to withstand a shock like falling and a vibration at the time of carrying and to have the extended lifetime.
For example, JP 2007-205491 A discloses a fan motor including a blade fixed to a rotating body and a bearing supporting the rotating body.
Conventional fan motors like one disclosed in JP 2007-205491 A have a rotating body with a blade and a static body.
When an acceleration is applied to the blade due to falling, etc., of the electronic device, the rotating body with the blade may contact the static body in the axial direction.
In general, when the rotating body and the static body contact with each other, those parts may be damaged in the worst case.
Alternatively, when the rotating body repeats contacting the static body, in general, the fan motor breaks down within a relatively short duration of use, and thus the lifetime thereof becomes short.
Moreover, according to such conventional fan motors, when the blade rotates, the blade receives force in the opposite direction to the direction of blowing.
When the blade receives such force, the rotating body with the blade travels in the axial direction, and thus the rotating body and the static body may contact with each other.
When the rotating body contacts the static body while the blade is rotating, the contacting portions are worn out, and may be damaged in the worst case, resulting in the reduction of the lifetime of the fan motor.
Moreover, when the rotating body contacts the static body while the blade is rotating, slide noises are generated from the fan motor. Such slide noises are unpleasant to the user of the electronic device.
Such a technical issue arises in the case of fan motors built in other various electronic devices in addition to the fan motors built in portable electronic devices.
The present invention has been made in view of the above-explained circumstance, and it is an object of the present invention to provide a technology of preventing a rotating body with a blade from contacting a static body or suppressing a reduction of the lifetime of a fan motor.
A first aspect of the present invention provides a fan motor that includes: a static body including a base; a rotating body which includes a shaft, a hub encircling a first end of the shaft and joined with the first end, and a blade joined around an outer periphery of the hub, and which rotates relative to the static body; a sleeve which retains thereinside a portion of the shaft at a second end side and which is joined with the base; a rotating flange which encircles at least a portion of the sleeve and which rotates together with the hub; a first static flange which is disposed in an area at a side of the first end of the shaft in an axial direction and which faces the rotating flange in the axial direction; a second static flange which is disposed in an area at a side of the second end of the shaft in the axial direction and which faces the rotating flange in the axial direction; a first dynamic pressure generating groove that is provided in either one of surfaces of the rotating flange and the first static flange facing with each other in the axial direction; a second dynamic pressure generating groove that is provided in either one of surfaces of the rotating flange and the second static flange facing with each other in the axial direction; and a lubricant present between the static body and the rotating body.
A second aspect of the present invention provides a fan motor that includes: a static body including a base; a rotating body which includes a shaft, a hub encircling a first end of the shaft and joined with the first end, and a blade joined around an outer periphery of the hub, and which rotates relative to the static body; a sleeve which retains thereinside a portion of the shaft at a second end side and which is joined with the base; a rotating flange which encircles at least a portion of the sleeve and which rotates together with the hub; a static flange which is disposed in an area at a side of the first end of the shaft in an axial direction with reference to the rotating flange and which is joined with the static body so as to overlap with the rotating flange in the radial direction; a dynamic pressure generating groove which is disposed outwardly of a portion of the sleeve retaining the shaft in the radial direction and which is provided in either one of surfaces of the static body and the rotating body facing with each other in the axial direction; and a lubricant present between the static body and the rotating body.
A third aspect of the present invention provides a fan motor that includes: a static body including a base; a rotating body which includes a shaft, a hub encircling a first end of the shaft and joined with the first end, and a blade joined around an outer periphery of the hub, and which rotates relative to the static body; a sleeve which retains thereinside a portion of the shaft at a second end side and which is joined with the base; a rotating flange which encircles at least a portion of the sleeve and which rotates together with the hub; a static flange which is disposed in an area at a side of the first end of the shaft in an axial direction with reference to the rotating flange, and which is joined with the static body so as to overlap the rotating flange in a radial direction; a dynamic pressure generating groove provided in either one of surfaces of the static body and the rotating body facing with each other in the axial direction; and a lubricant present between the static body and the rotating body.
Any combination of the above-explained structural elements and mutual replacement of the structural elements and expressions of the present invention among a method, a device, and a system, etc., are also effective as an embodiment of the present invention.
A preferred embodiment of the present invention will be explained below with reference to the accompanying drawings.
The same or equivalent structural element or member shown in respective figures will be denoted by the same reference numeral and the duplicated explanation thereof will be omitted accordingly.
The dimension of a member in each figure is enlarged or reduced as needed in order to facilitate understanding.
A part of a member not important to explain the embodiment will be also omitted in each figure.
A fan motor of an embodiment is appropriate as a fan motor built in an electronic device like a personal computer.
The fan motor 100 includes a static body 2 and a rotating body 4.
The static body 2 includes a base 6 and an outer periphery wall 16.
The rotating body 4 includes a shaft 8, a hub 10, and a blade unit 12.
The shaft 8 has a first end 8A that is shown in
The explanation below will be given based on a definition that the first end 8A of the shaft 8 is an upper side with respect to the second end 8B thereof.
However, the posture of the fan motor of the present invention when in use is not limited to this definition.
The fan motor of the present invention can be used in any arbitrary posture.
The blade unit 12 includes a blade base 18 and, for example, 10 blades 14. The number of blades can be changed as needed depending on the application, the rotating speed, etc., of the fan motor 100.
The blade base 18 includes a cylinder part 18A, a disc part 18B, and a through hole 18C.
The cylinder part 18A is a hollow cylinder.
The disc part 18B protrudes inwardly of the radial direction from the upper end of the cylinder part 18A.
The through hole 18C is disposed at the center of the disc part 18B.
The 10 blades 14 protrude outwardly of the radial direction from the outer periphery of the cylinder part 18A and are fixed thereto.
The blades 14 are disposed at a substantially equal interval in the circumferential direction.
The blade unit 12 is formed of a resin material like polycarbonate by molding.
The blade unit 12 may contain glass fibers at a predetermined ratio.
The blade unit 12 has an outer diameter of, for example, 30 mm and a height of, for example, 5 mm.
The blade unit 12 has the blade base 18 fixed to the hub 10 by bonding.
The blade unit 12 may be fixed to the hub 10 by other techniques.
The outer periphery wall 16 has a substantially rectangular external shape and an opening 16B located at the center thereof, and encircles the blade unit 12.
The outer periphery wall 16 is formed of a resin material like polycarbonate by molding.
The outer periphery wall 16 may contain glass fibers at a predetermined ratio.
The outer periphery wall 16 has a recess 16A in an end face in the axial direction.
The base 6 is fitted in the recess 16A of the outer periphery wall 16 and fixed to the outer periphery wall 16 by bonding.
Hence, indication of a reference numeral to a portion of the same element at one side in the horizontal direction will be omitted in
The static body 2 further includes a sleeve 20, a first static flange 24, a second static flange 26, a housing 28, a stator core 58, a core holder 62, coils 60, and a magnetic ring 44.
The rotating body 4 further includes a rotating flange 22.
The rotating flange 22 encircles the sleeve 20, and is fixed to the hub 10.
The sleeve 20 encircles the shaft 8.
The sleeve 20 is surrounded by the housing 28 and is fixed thereto.
The housing 28 is fixed to the base 6.
The first static flange 24 is fixed to the sleeve 20, and is located above the rotating flange 22 in the axial direction via a clearance.
The second static flange 26 is fixed to the housing 28, and is located below the rotating flange 22 in the axial direction via a clearance.
Hence, the rotating flange 22 is rotatable in a space defined by the clearances with the first static flange 24 and with the second static flange 26 in the axial direction.
The hub 10 includes an external wall 10A, a disc part 10B, a through hole 10C, and a first cylinder part 36.
The external wall 10A is in a hollow cylindrical shape.
The disc part 10B protrudes inwardly of the radial direction from the upper end of the external wall 10A.
The through hole 10C is provided at the center of the disc part 10B.
The hub 10 is formed of a soft magnetic material like SUS430F.
The hub 10 is formed in a predetermined shape by, for example, cutting.
The hub 10 may be shaped by pressing instead of cutting.
The hub 10 has the external wall 10A fitted inwardly of the cylinder part 18A of the blade base 18.
The hub 10 has the disc part 10B abutting the lower face of the disc part 10B of the blade base 18.
The hub 10 has the through hole 10C where the first end 8A of the shaft 8 is inserted.
The first cylinder part 36 protrudes downwardly from the disc part 10B in the axial direction.
The first cylinder part 36 has the inner periphery coaxial with the through hole 10C.
The first cylinder part 36 encircles and fastens a second cylinder part 38 to be discussed later.
According to the fan motor 100 of this embodiment, the hub 10 has, for example, six boss holes 10D, and the blade base 18 has, for example, six bosses 18D.
The six boss holes 10D pass all the way through the disc part 10B in the axial direction.
The six boss holes 10D are disposed in the circumferential direction at a substantially equal interval.
Conversely, the bosses 18D are provided at positions corresponding to respective boss holes 10D.
The bosses 18D protrude downwardly from the disc part 18B in the axial direction.
The bosses 18D each include a boss protrusion 18E and a boss thicker part 18F.
The boss protrusion 18E passes all the way through the boss hole 10D and protrudes from the lower face of the disc part 10B.
The boss thicker part 18F is fixed to the tip of the boss protrusion 18E, and has a larger diameter than that of the boss hole 10D.
The boss thicker part 18F can be formed by heating the tip of the boss protrusion 18E to let the tip deformed.
That is, the boss 18D, the boss protrusion 18E, and the boss thicker part 18F are continuous in a seamless manner.
Such a configuration restricts the traveling of the blade base 18 in the axial direction relative to the hub 10.
Returning to
The rotating flange 22 encircles the sleeve 20, and rotates together with the rotating body 4.
The rotating flange 22 includes a second cylinder part 38 protruding downwardly from the outer periphery of the rotating flange 22.
The rotating flange 22 and the second cylinder part 38 are joined together in a seamless manner.
That is, the rotating flange 22 and the second cylinder part 38 are an annular member having a cross section of a reversed L shape.
The rotating flange 22 is formed of an iron-and-steel material like SUS430F by, for example, cutting.
The rotating flange 22 may be formed of a metal by pressing. Alternatively, the rotating flange 22 may be formed of a resin material by molding. The rotating flange 22 rotates in a space defined by the first static flange 24 and the second static flange 26 in the axial direction.
The second cylinder part 38 has the outer periphery fixed to the inner periphery of the first cylinder part 36 by bonding.
A magnet 40 in a ring shape is fixed inwardly of the external wall 10A of the hub 10 by bonding.
The magnet 40 contains materials, such as neodymium, iron, and born.
The magnet 40 has a surface on which an anti-corrosive process is applied like electrodeposition coating or spray coating.
The magnet 40 has driving magnetic poles of, for example, 16 poles disposed in the circumferential direction on the inner periphery of the magnet 40.
The magnet 40 has the inner periphery facing twelve tips 58C of a stator core 58 to be discussed later in the radial direction.
The shaft 8 is formed of an iron-and-steel material like stainless steel in an elongated cylindrical shape.
The shaft 8 has the first end 8A fitted in the through hole 10C of the hub 10 and fixed thereto by bonding.
The shaft 8 has the second end 8B retained in the sleeve 20 and supported in a freely rotatable manner.
The sleeve 20 includes a cylinder part 20A.
The cylinder part 20A is a hollow cylinder.
The first static flange 24 extends outwardly of the radial direction from the upper part of the cylinder part 20A.
The cylinder part 20A and the first static flange 24 are formed together with each other.
That is, the first static flange 24 is joined with the cylinder part 20A in a seamless manner.
The first static flange 24 and the cylinder part 20A are formed of a metal like brass by, for example, cutting.
The first static flange 24 and the cylinder part 20A have, for example, an electroless nickel plating layer on the surface thereof.
The first static flange 24 and the cylinder part 20A may be formed of a resin material by molding.
The cylinder part 20A retains the second end 8B of the shaft 8 and supports the second end 8B in a freely rotatable manner.
The housing 28 includes a cylinder part 28A and a bottom 28C.
The cylinder part 28A is a hollow cylinder.
The second static flange 26 is fixed to an upper end of the cylinder part 28A.
The bottom 28C is fixed to the lower end face of the cylinder part 28A, and covers the lower end face thereof.
The second static flange 26, the cylinder part 28A, and the bottom 28C are formed together.
That is, the second static flange 26, the cylinder part 28A, and the bottom 28C are joined together in a seamless manner.
The second static flange 26, the cylinder part 28A, and the bottom 28C are formed of a metal like brass by, for example, cutting.
The second static flange 26, the cylinder part 28A, and the bottom 28C have, for example, electroless nickel plating layer on the surface thereof. The second static flange 26, the cylinder part 28A, and the bottom 28C may be formed of a resin material by molding.
The outer periphery of the cylinder part 20A of the sleeve 20 is fitted in and bonded with the inner periphery of the cylinder part 28A and thus the housing 28 fixes the sleeve 20.
That is, the housing 28 has the cylinder part 28A encircling the cylinder part 20A of the sleeve 20.
The second static flange 26 is located below the first static flange 24 in the axial direction with a space.
The housing 28 is fitted in a base hole 6A and fixed therewith by bonding.
The base 6 has a substantially rectangular external shape, and has the base hole 6A passing all the way through in the axial direction at the center of the base 6.
The base 6 has ventilation slots in an area facing the blades 14 in the axial direction.
The base 6 has a core layer mainly composed of, for example, iron, and a surface layer mainly composed of, for example, zinc adhered to the surface of the core layer.
The base 6 is formed of a cold-rolled steel plate with a zinc plating in a predetermined shape by, for example, pressing.
The base 6 may be formed of the other materials like a stainless steel.
The edge of the base hole 6A and the housing 28 have, for example, a welded part 42 joined by welding.
The welded part 42 is in a ring shape along the edge of the base hole 6A.
A pair of radial dynamic pressure generating grooves 50 and 52 are disposed in the inner periphery of the cylinder part 20A of the sleeve 20.
The radial dynamic pressure generating grooves 50 and 52 may be disposed in an outer periphery 8BA of the shaft 8.
The radial dynamic pressure generating grooves 50 and 52 are in, for example, a herringbone shape.
However, those grooves may be in the other shapes like a spiral shape.
A lubricant 34 is present between the sleeve 20 and the shaft 8.
A first dynamic pressure generating groove 54 is disposed in a surface of the rotating flange 22 facing with the first static flange 24 in the axial direction.
The first dynamic pressure generating groove 54 may be disposed in a surface of the first static flange 24 facing with the rotating flange 22 in the axial direction.
A second dynamic pressure generating groove 56 is disposed in a surface of the rotating flange 22 facing with the second static flange 26 in the axial direction.
The second dynamic pressure generating groove 56 may be disposed in a surface of the second static flange 26 facing with the rotating flange 22 in the axial direction.
The first and second dynamic pressure generating grooves 54 and 56 are formed in, for example, a herringbone shape.
The first and second dynamic pressure generating grooves 54 and 56 may be in the other shapes like a spiral shape.
The lubricant 34 is also present between the first static flange 24 and the rotating flange 22 and between the second static flange 26 and the rotating flange 22.
When the shaft 8 and the rotating flange 22 rotate, the radial dynamic pressure generating grooves 50, 52, the first dynamic pressure generating groove 54, and the second dynamic pressure generating groove 56 respectively generate dynamic pressures applied to the lubricant 34.
A capillary seal 46 is located at a space between the inner periphery of the second cylinder part 38 and the outer periphery of the housing 28 in the radial direction.
The lubricant 34 is continuously present in spaces between the upper face of the bottom 28C of the housing 28 and the sleeve 20 and the shaft 8, a space between the first static flange 24 and the rotating flange 22, a space between the second static flange 26 and the rotating flange 22, and a space between the second cylinder part 38 and the housing 28.
An air-liquid interface 34A of the lubricant 34 contacts both of the inner periphery of the second cylinder part 38 and the outer periphery of the housing 28 in the capillary seal 46.
The capillary seal 46 has a wide space in the axial direction which is close to the second end 8B of the shaft 8.
Hence, the capillary seal 46 can suppress a leak-out of the lubricant 34 by capillary force.
The static body 2 further has a communicated passage BP of the lubricant 34.
The communicated passage BP communicates the capillary seal 46 with a space above the bottom 28C of the housing 28.
By employing such a structure, the communicated passage BP suppresses a pressure difference in the lubricant 34 between the capillary seal 46 and the space above the bottom 28C of the housing 28.
The sleeve 20 has a recess 20B formed in the outer periphery of the sleeve 20 and continuous in the direction along the rotation axis R.
The recess 20B is filled with the lubricant 34, and is a part of the communicated passage BP.
That is, the communicated passage BP of the lubricant 34 includes the recess 20B.
The housing 28 may have a passage that is a part of the communicated passage BP instead of the sleeve 20.
Returning to
The magnetic ring 44 is formed of, for example, a magnetic steel plate by pressing.
The magnetic ring 44 is located at an area outwardly of the stator core 58 in the radial direction.
The magnetic ring 44 faces a lower end face 40A of the magnet 40 in the axial direction, and is fixed to the base 6 by bonding.
The magnetic ring 44 may be fixed to the base 6 by caulking.
The magnetic ring 44 causes the magnet 40 to have magnetic suction force in the direction toward the base 6.
As a result, the blades 14 are pushed down in the direction toward the base 6, and it becomes possible to prevent the blades 14 from floating because of reactive force of airflows produced by the blades 14.
The magnetic ring 44 may be joined together with the base 6 in a seamless manner.
The stator core 58 includes a core annular part 58A, for example, twelve core teeth 58B and a core tip 58C.
The core annular part 58A is in a ring shape surrounding the center hole.
The twelve core teeth 58B protrude outwardly of the radial direction from the outer periphery of the core annular part 58A.
The twelve core teeth 58B are arranged at, for example, substantially equal interval in the circumferential direction.
The core tip 58C extends outwardly of the radial direction at respective outer peripheries of the core teeth 58B.
The stator core 58 is fixed to an upper face of the base 6 by means of a core holder 62 to be discussed later.
The stator core 58 is formed by stacking and caulking, for example, six thin electromagnetic steel plates together.
The core teeth 58B are surrounded by a cover 62C to be discussed later.
The stator core 58 may have an insulative layer formed on the surface thereof.
Such an insulative layer is formed by, for example, electrodeposition coating, or powder coating.
The coil 60 is provided at each of the core teeth 58B of the stator core 58.
The coil 60 is formed by winding, for example, an electrical wire covered with an insulative material like poly urethane around each of the core teeth 58B.
The coil 60 is coupled to a predetermined drive circuit.
When a drive current of a three-phase substantially sinusoidal wave is caused to flow through the coil 60, drive magnetic fluxes are generated along the core tip 58C.
The core holder 62 includes a mount 62A, a cover 62C, and for example, six spacers 62D.
The mount 62A joins the cover 62C and the six spacers 62D in a seamless manner.
The mount 62A, the cover 62C, and the six spacers 62D may be formed separately and joined together later.
The core holder 62 is formed of a resin material like poly-carbonate by molding.
The core holder 62 may contain glass fibers, etc., at a predetermined ratio.
The mount 62A is formed in, for example, a substantially annular shape.
The mount 62A may be in other shapes.
The mount 62A surrounds the housing 28.
The mount 62A is present between the core annular part 58A and the base 6 in the axial direction.
The spacer 62D is present between the core tip 58C and the base 6 in the axial direction.
The six spacers 62D are each in a substantially cylindrical shape, and disposed in the circumferential direction at a substantially equal interval.
The spacer 62D has a protrusion 62E and a stopper 62F.
The core teeth 58B is fastened to the cover 62C, thereby fastening the stator core 58 to the core holder 62.
The base 6 has a holder hole 6B at a location corresponding to each of the spacers 62D.
The holder hole 6B passes all the way through the base 6 in the axial direction, and includes a smaller diameter part and a larger diameter part successive from the lower portion of the smaller diameter part.
The spacer 62D has the protrusion 62E passing all the way through the holder hole 6B.
The stopper 62F is retained in the larger diameter part of the holder hole 6B, and has a larger diameter than the minimum diameter of the holder hole 6B.
The stopper 62F can be formed by heating the protrusion 62E to be deformed.
According to such a structure, the stator core 58 and the core holder 62 are fixed to the base 6.
Next, an explanation will be given of an operation of the fan motor 100 employing the above-explained structure together with an advantage thereof.
In order to rotate the blades 14, a drive current of a three-phase substantially sinusoidal wave is supplied from the predetermined drive circuit to the coils 60.
As a result, the drive magnetic fluxes are generated along the core tip 58C.
Such magnetic fluxes give a torque to the magnet 40, and the blades 14 and the hub 10 fastened to the magnet 40 start rotating by that torque.
For example, the blades 14 generate airflows downwardly of the axial direction by their own rotation.
The blades 14 may generate airflows upwardly of the axial direction by their own rotation.
When the hub 10 starts rotating, the joined portion between the hub 10 and the blade base 18 receives force in the direction of rotation. Hence, when the hub 10 repeats rotating and stopping inherent to the use of the fan motor 100, the force in the direction of rotation may mutually displace the hub 10 and the blade base 18, and such a joined portion may be damaged.
However, according to the fan motor 100 of this embodiment, the hub 10 has the six boss holes 10D and the blade base 18 has the six bosses 18D.
Since each boss 18D passes all the way through each boss hole 10D, the mutual displacement of the blade base 18 to the hub 10 in the direction of rotation can be restricted.
Accordingly, even if the force in the direction of rotation is applied to the joined portion between the hub 10 and the blade base 18, the hub 10 and the blade base 18 are fastened together and are capable of withstanding such a force. Hence, the possibility that the joined portion is damaged can be reduced.
When the shaft 8 and the rotating flange 22 rotate, the radial dynamic pressure generating grooves 50, 52, and the first and second dynamic pressure generating grooves 54, 56 respectively generate dynamic pressures applied to the lubricant 34, and such dynamic pressures support the rotating body 4 with the blades 14 in the radial direction and in the axial direction.
In general, when the diameter of a dynamic pressure generating groove is reduced, the dynamic pressure to be generated becomes small. This brings about the reduction of the rigidity of a bearing, and the possibility that the rotating body and the static body contact increases.
According to the fan motor 100 of this embodiment, the rotating flange 22 is located outwardly of the radial direction from the cylinder part 20A of the sleeve 20.
Hence, the first and second dynamic pressure generating grooves 54 and 56 are located outwardly of the shaft 8 or the cylinder part 20A of the sleeve 20 in the radial direction.
Accordingly, respective diameters of the first and second dynamic pressure generating grooves 54, 56 can be increased. As a result, the dynamic pressure to be generated is increased to support the rotating body 4 with the blades 14 in the radial direction and in the axial direction in a non-contact manner with the static body 2, and to increase the rigidity of the bearing. Moreover, the non-contact condition results in a suppression of the generation of slide noises.
Moreover, in the rotating operation, the blades 14 may receive an acceleration in a direction departing from the base 6 in the axial direction. In this case, the rotating body 4 with the blades 14 may move in the direction departing from the base 6 in the axial direction, and respective faces of the static body 2 and the rotating body 4 facing with each other in the axial direction may contact with each other. In the worst case, the fan motor 100 breaks down if such a contact repeats.
According to the fan motor 100 of this embodiment, however, the first and second dynamic pressure generating grooves 54 and 56 are provided in both faces of the rotating flange 22 in the axial direction.
As explained above, the first and second dynamic pressure generating grooves 54 and 56 support the rotating body 4 with the blades 14 in a non-contact manner with the static body 2 in the axial direction at the time of the rotating operation, and thus the possibility that the rotating body 4 contacts the static body 2 can be reduced.
It is presumed that an end of the shaft 8 where the rotating body 4 with the blades 14 is joined is an output end of the shaft 8. In this case, according to the fan motor 100 of this embodiment, the first end 8A is the output end.
According to a design of disposing a dynamic pressure generating groove at an area distant from the output end of the shaft in the axial direction, the shaft has a high possibility of precessing when rotating.
When the shaft precesses, the wear of the shaft or the sleeve may increase, resulting in the reduction of the lifetime of the fan motor.
However, according to the fan motor 100 of this embodiment, the rotating flange 22 is disposed at an area close to the first end 8A of the shaft 8 rather than the second end 8B thereof in the axial direction.
Hence, the first and second dynamic pressure generating grooves 54 and 56 are located at respective areas close to the first end 8A of the shaft 8 rather than the second end 8B thereof in the axial direction.
As a result, the possibility that the shaft 8 precesses can be reduced, thereby suppressing the reduction of the lifetime of the fan motor 100.
In addition, according to the fan motor 100 of this embodiment, the rotating flange 22 is located at an area close to the first end 8A of the shaft 8 rather than the weighted center G of the rotating body 4 in the axial direction.
Since the rotating flange 22 is distant from the second end 8B of the shaft 8, the principle of leverage acts, and the rotating flange 22 together with the first and second static flanges 24 and 26 can suppress the precession movement of the shaft 8, i.e., the wobbling of the rotating body 4 in the rotational direction.
According to such a configuration, the rotating flange 22 can support, together with the first and second static flanges 24 and 26, an off-centered load by contacting one another when the fan motor 100 is not rotating and when the off-centered load is applied to the blades 14.
When the fan motor has a dimension in the axial direction constant and the rotating flange is fixed to the shaft, the dimension of the radial dynamic pressure generating groove in the axial direction decreases by what corresponds to such a configuration, resulting in the reduction of the bearing rigidity in some cases.
However, according to the fan motor 100 of this embodiment, the rotating flange 22 is fixed to the hub 10, and thus it does not bring about the reduction of the bearing rigidity.
The embodiment of the present invention was explained above, but the present invention is not limited to the above-explained embodiment. Various changes and modifications can be made without departing from the scope and spirit of the present invention.
