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United States Patent Application 20170356466
Kind Code A1
Hino; Yuko ;   et al. December 14, 2017

BLOWER APPARATUS

Abstract

This blower apparatus includes an air blowing portion including a plurality of flat plates arranged with an axial gap defined between adjacent ones of the flat plates; a motor portion arranged to rotate the air blowing portion; and a housing arranged to house the air blowing portion and the motor portion. The housing includes an air inlet and an air outlet. At least one of the flat plates includes a plurality of through holes each of which is arranged to pass therethrough in the axial direction. An air flow traveling radially outward is generated between the flat plates by viscous drag of surfaces of the flat, plates and a centrifugal force. Since the air flow is generated between the flat plates, the air flow does not easily leak upwardly or downwardly.


Inventors: Hino; Yuko; (Kyoto, JP) ; Yoo; Seung-Sin; (Kyoto, JP) ; Tsukamoto; Tomoyuki; (Kyoto, JP) ; Makita; Akihiko; (Kyoto, JP)
Applicant:
Name City State Country Type

Nidec Corporation

Kyoto

JP
Assignee: Nidec Corporation
Kyoto
JP

Family ID: 1000002682485
Appl. No.: 15/615234
Filed: June 6, 2017


Related U.S. Patent Documents

Application NumberFiling DatePatent Number
62347380Jun 8, 2016

Current U.S. Class: 1/1
Current CPC Class: F04D 29/626 20130101; F04B 35/04 20130101; F04B 17/00 20130101; F04D 29/083 20130101; F04D 25/06 20130101
International Class: F04D 29/62 20060101 F04D029/62; F04D 29/08 20060101 F04D029/08; F04B 35/04 20060101 F04B035/04; F04D 25/06 20060101 F04D025/06

Foreign Application Data

DateCodeApplication Number
Mar 15, 2017JP2017-049388

Claims



1. A blower apparatus comprising: an air blowing portion arranged to rotate about a central axis extending in a vertical direction; a motor portion arranged to rotate the air blowing portion; and a housing arranged to house the air blowing portion and the motor portion; wherein the housing includes: an air inlet arranged above the air blowing portion, and arranged to pass through a portion of the housing in an axial direction; and an air outlet arranged to face in a radial direction at least one circumferential position radially outside of the air blowing portion; the air blowing portion includes a plurality of flat plates arranged in the axial direction with an axial gap defined between adjacent ones of the flat plates; and at least one of the flat plates includes a plurality of through holes each of which is arranged to pass therethrough in the axial direction.

2. The blower apparatus according to claim 1, wherein at least one of the flat plates includes an air hole arranged to pass therethrough in the axial direction; each air hole is arranged to be in communication with a space radially outside of the air blowing portion through the axial gap; and each of the through holes is arranged radially outward of the air hole.

3. The blower apparatus according to claim 2, wherein each through hole is arranged to have an opening area smaller than an opening area of the air hole.

4. The blower apparatus according to claim 2, wherein at least one of the flat plates includes: the air hole; and an air blowing region being a region radially outside of the air hole; and each of the through holes is arranged radially outward of a radial middle of the air blowing region.

5. The blower apparatus according to claim 2, wherein at least one of the flat plates includes: the air hole; and an air blowing region being a region radially outside of the air hole; and each of the through holes is arranged radially inward of a radial middle of the air blowing region,

6. The blower apparatus according to claim 1, wherein at least one of the flat plates includes: an inner annular portion being annular, and centered on the central axis; an outer annular portion being annular, centered on the central axis, and arranged radially outside of the inner annular portion; a plurality of ribs each of which is arranged to radially join the inner annular portion and the outer annular portion to each other; and a plurality of air holes each of which is surrounded by the inner annular portion, the outer annular portion, and two circumferentially adjacent ones of the ribs, and is arranged to pass through the flat plate in the axial direction; and a line that joins circumferential middle points of each through hole is arranged to extend radially outward with a curvature substantially equal to a curvature with which each rib is arranged to extend radially outward.

7. The blower apparatus according to claim 1, wherein at least one of the flat plates includes: an inner annular portion being annular, and centered on the central axis; an outer annular portion being annular, centered on the central axis, and arranged radially outside of the inner annular portion; a plurality of ribs each of which is arranged to radially join the inner annular portion and the outer annular portion to each other; and a plurality of air holes each of which is surrounded by the inner annular portion, the outer annular portion, and two circumferentially adjacent ones of the ribs, and is arranged to pass through the flat plate in the axial direction; and each of the through holes is arranged on a radially outer extension of a separate one of the ribs.

8. The blower apparatus according to claim 1, wherein each through hole is in a shape of a tear drop or an airfoil when viewed in the axial direction.

9. The blower apparatus according to claim 1, wherein the through holes are arranged at regular intervals in a circumferential direction.

10. The blower apparatus according to claim 1, wherein, the through holes include: a plurality of first through holes each of which is at a first distance from the central axis; and a plurality of second through holes each of which is at a second distance from the central axis, the second distance being different from the first distance; and each of the first through holes is arranged at a circumferential position different from a circumferential position of each of the second through holes.

11. The blower apparatus according to claim 1, wherein a center of the air inlet is arranged to coincide with the central axis.

12. The blower apparatus according to claim 1, wherein the motor portion includes: a stationary portion including an armature and a bearing housing; and a rotating portion including a shaft, a bearing member, and a magnet arranged radially opposite to the armature; the bearing housing and a combination of the shaft and the bearing member are arranged to have a lubricating fluid therebetween; the bearing housing and the rotating portion are arranged to together define a gap defining a seal portion therebetween, the seal portion having a surface of the lubricating fluid defined therein; and in the seal portion, a distance between the bearing housing and rotating portion is arranged to increase with increasing distance from the surface of the lubricating field.

13. The blower apparatus according to claim 1, wherein the motor portion includes: a stationary portion including an armature; a rotating portion including a magnet arranged radially opposite to the armature; and a ball bearing arranged to connect the rotating portion to the stationary portion such that the rotating portion is rotatable with respect to the stationary portion.

14. The blower apparatus according to claim 1, wherein the housing includes a plurality of the air outlets at a plurality of circumferential positions.
Description



BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to a blower apparatus.

2. Description of the Related Art

[0002] A centrifugal blower apparatus which generates an air flow traveling radially outward by rotating an impeller including a plurality of blades is known. A known blower apparatus including an impeller is described in, for example, JP-A 2008-88985.

[0003] In the blower apparatus described in JP-A 2008-88985, a plurality of blades referred to as fan blades push surrounding gas to generate air flows traveling radially outward.

SUMMARY OF THE INVENTION

[0004] In recent years, there has still been a demand for reductions in the size and thickness of electronic devices. Accordingly, there has also been a demand for a reduction in the thickness of blower apparatuses used to cool the interiors of the electronic devices.

[0005] Here, in the case where an impeller is used to generate air flows, as in the blower apparatus described in JP-A 2008-88985, air flows pushed by a blade leak from axially upper and lower ends of the blade while the impeller is rotating. As a result, air pressure is lower at the axially upper and lower ends of the blade than in the vicinity of an axial middle of the blade. Accordingly, a reduction in the thickness of the blower apparatus, which involves a reduction in the axial dimension of the impeller, will result in a failure to secure sufficient air blowing efficiency.

[0006] In addition, there has been a demand for a reduction in weight, in addition to thickness, of blower apparatuses installed in electronic devices or the like.

[0007] An object of the present invention is to provide a technique for achieving a reduction in weight of a centrifugal blower apparatus which is excellent in air blowing efficiency.

[0008] A blower apparatus according to a preferred embodiment of the present invention includes an air blowing portion arranged to rotate about a central axis extending in a vertical direction; a motor portion arranged to rotate the air blowing portion; and a housing arranged to house the air blowing portion and the motor portion. The housing includes an air inlet arranged above the air blowing portion, and arranged to pass through a portion of the housing in an axial direction; and an air outlet arranged to face in a radial direction at least one circumferential position radially outside of the air blowing portion. The air blowing portion includes a plurality of flat plates arranged in the axial direction with an axial gap defined between adjacent ones of the flat plates. At least one of the flat plates includes a plurality of through holes each of which is arranged to pass therethrough in the axial direction.

[0009] According to the above preferred embodiment of the present invention, once the air blowing portion starts rotating, an air flow traveling radially outward is generated in the axial gap between the adjacent ones of the flat plates by viscous drag of surfaces of the flat plates and a centrifugal force. Thus, gas supplied through the air inlet and the air hole travels radially outwardly of the air blowing portion. Since the air flow is generated between the flat plates, the air flow does not easily leak upwardly or downwardly, and thus, an improvement in air blowing efficiency is achieved. Accordingly, a reduced thickness of the blower apparatus according to the above preferred embodiment of the present invention does not result in a significant reduction in the air blowing efficiency. In addition, the through holes of the flat plate(s) reduce weight of the air blowing portion. That is, a reduction in weight of the blower apparatus is achieved. In addition, the blower apparatus according to the above preferred embodiment of the present invention is superior to a comparable centrifugal fan including an impeller in terms of being silent.

[0010] The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a perspective view of a blower apparatus according to a first preferred embodiment of the present invention.

[0012] FIG. 2 is a top view of the blower apparatus according to the first preferred embodiment.

[0013] FIG. 3 is a sectional view of the blower apparatus according to the first, preferred embodiment.

[0014] FIG. 4 is an exploded perspective view of the blower apparatus according to the first preferred embodiment.

[0015] FIG. 5 is a partial sectional view of the blower apparatus according to the first preferred embodiment.

[0016] FIG. 6 is a top view of a plurality of flat plates of the blower apparatus according to the first preferred embodiment.

[0017] FIG. 7 is a top view of a plurality of flat plates of a blower apparatus according to a modification of the first preferred embodiment.

[0018] FIG. 8 is a top view of a plurality of flat plates of a blower apparatus according to a modification of the first preferred embodiment.

[0019] FIG. 9 is a top view of a plurality of flat plates of a blower apparatus according to a modification of the first preferred embodiment.

[0020] FIG. 10 is a top view of a plurality of flat plates of a blower apparatus according to a modification of the first preferred embodiment.

[0021] FIG. 11 is a top view of a plurality of flat plates of a blower apparatus according to a modification of the first preferred embodiment.

[0022] FIG. 12 is a top view of a plurality of flat plates of a blower apparatus according to a modification of the first preferred embodiment.

[0023] FIG. 13 is a top view of a plurality of flat plates of a blower apparatus according to a modification of the first preferred embodiment.

[0024] FIG. 14 is a partial sectional view of a blower apparatus according to a modification of the first preferred embodiment.

[0025] FIG. 15 is a top view of a blower apparatus according to a modification of the first preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, blower apparatuses according to preferred embodiments of the present invention will be described. It is assumed herein that a side on which an upper plate portion is arranged with respect to a lower plate portion is an upper side, and the shape of each member or portion and relative positions of different members or portions will be described based on the above assumption. It should be noted, however, that the above definition of the upper and lower sides is not meant to restrict in any way the orientation of a blower apparatus according to any preferred embodiment of the present invention at the time of manufacture or when in use.

1. FIRST PREFERRED EMBODIMENT

[0027] 1-1. Structure of Blower Apparatus

[0028] FIG. 1 is a perspective view of a blower apparatus 1 according to a first preferred embodiment of the present invention. FIG. 2 is a top view of the blower apparatus 1. FIG. 3 is a sectional view of the blower apparatus 1 taken along line A-A in FIG. 2. FIG. 4 is an exploded perspective view of the blower apparatus 1. FIG. 5 is a partial sectional view of the blower apparatus 1. The blower apparatus 1 is a centrifugal blower apparatus designed to generate an air flow traveling radially outward by rotating an air blowing portion 40. The blower apparatus 1 is, for example, installed in an electronic device, such as, for example, a personal computer, to cool an interior thereof. Note that blower apparatuses according to preferred embodiments of the present invention may be used for other purposes.

[0029] Referring to FIGS. 1 to 4, the blower apparatus 1 includes a housing 20, a motor portion 30, and the air blowing portion 40.

[0030] The housing 20 is a case arranged to house the motor portion 30 and the air blowing portion 40. The housing 20 includes a lower plate portion 21, a side wall portion 22, and an upper plate portion 23.

[0031] The lower plate portion 21 is arranged to define a bottom portion of the housing 20. The lower plate portion 21 is arranged to extend radially below the air blowing portion 40 to cover at least a portion of a lower side of the air blowing portion 40. In addition, the lower plate portion 21 is arranged to support the motor portion 30.

[0032] The side wall portion 22 is arranged to extend upward from the lower plate portion 21. The side wall portion 22 is arranged to cover a lateral side of the air blowing portion 40 between the lower plate portion 21 and the upper plate portion 23. In addition, the side wall portion 22 includes an air outlet 201 arranged to face in a radial direction at one circumferential position. In the present preferred embodiment, the lower plate portion 21 and the side wall portion 22 are defined integrally with each other. Mote that the lower plate portion 21 and the side wall portion 22 may alternatively be defined by separate members.

[0033] The upper plate portion 23 is arranged to define a cover portion of the housing 20. The upper plate portion 23 is arranged to extend radially above the lower plate portion 21. In addition, the upper plate portion 23 includes an air inlet 202 arranged to pass therethrough in an axial direction. In other words, the upper plate portion 23 includes an inner edge portion 231 arranged to define the air inlet 202. The air inlet 202 is, for example, circular and is centered on a central axis 9 in a plan view.

[0034] The motor portion 30 is a driving portion arranged to rotate the air blowing portion 40. Referring to FIG. 5, the motor portion 30 includes a stationary portion 31 and a rotating portion 32. The stationary portion 31 is fixed to the lower plate portion 21. The stationary portion 31 is thus arranged to be stationary relative to the housing 20. The rotating portion 32 is supported to be rotatable about the central axis 9 with respect to the stationary portion 31.

[0035] The stationary portion 31 includes a stator fixing portion 311, a stator 312, and a bearing housing 313.

[0036] The stator fixing portion 311 is fitted in a fixing hole 211 defined in the lower plate portion 21. As a result, the stator fixing portion 311 is fixed to the lower plate portion 21. The stator fixing portion 311 is arranged to extend upward from the fixing hole 211 to assume a cylindrical shape with the central axis 9 as a center thereof. The stator 312 is fixed to an outer circumferential portion of an upper portion of the stator fixing portion 311.

[0037] The stator 312 is an armature arranged to generate magnetic flux in accordance with electric drive currents supplied from an external source. The stator 312 is arranged to annularly surround the central axis 9, which extends in a vertical direction. The stator 312 includes, for example, an annular stator core defined by laminated steel sheets, and conducting wires wound around the stator core.

[0038] The bearing housing 313 is a member being cylindrical and having a closed bottom. Specifically, the bearing housing 313 includes a disk-shaped bottom, portion, and a cylindrical portion arranged to extend upward from the bottom portion. The bearing housing 313 is fixed to an inner circumferential surface of the stator fixing portion 311.

[0039] The rotating portion 32 includes a shaft 321, a hub 322, a bearing member 323, and a magnet 324.

[0040] The shaft 321 is a member arranged to extend along the central axis 9. The shaft 321 according to the present preferred embodiment includes a columnar portion arranged inside of a first cylindrical portion 512, which will be described below, and arranged to extend with the central axis 9 as a center thereof, and a disk-shaped portion arranged to extend radially from a lower end portion of the columnar portion.

[0041] The hub 322 is fixed to the shaft 321. The hub 322 is made up of a hub body member 51 and a flange member 52.

[0042] The hub body member 51 includes a first top plate portion 511, the first cylindrical portion 512, a second cylindrical portion 513, and a magnet holding portion 514.

[0043] The first top plate portion 511 is a disk-shaped portion arranged to extend radially with the central axis 9 as a center thereof. The first top plate portion 511 is arranged above the stator 312. The first top plate portion 511 has a recessed portion 515 recessed from an upper surface thereof at an outer edge portion thereof.

[0044] The first cylindrical portion 512 is arranged to extend downward from the first top plate portion 511 to assume a cylindrical shape with the central axis 9 as a center thereof. The columnar portion of the shaft 321 is housed in the first cylindrical portion 512. In addition, the shaft 321 is fixed to the first cylindrical portion 512.

[0045] The second cylindrical portion 513 is arranged to extend downward from the first top plate portion 511 to assume a cylindrical shape with the central axis 9 as a center thereof. The second cylindrical portion 513 is arranged to have an inside diameter greater than an outside diameter of the first cylindrical portion 512. In other words, the second cylindrical portion 513 is arranged radially outside of the first cylindrical portion 512.

[0046] The magnet holding portion 514 is arranged to extend downward from a radially outer end of the first top plate portion 511 to assume a cylindrical shape with the central axis 9 as a center thereof. The magnet holding portion 514 is arranged radially outside of the stator 312. The magnet 324 is fixed to an inner circumferential surface of the magnet holding portion 514.

[0047] The flange member 52 includes an outer wall portion 521, a second top plate portion 522, and a flat plate holding portion 523.

[0048] The outer wall portion 521 is a cylindrical portion arranged to extend in the vertical direction with the central axis 9 as a center thereof. The outer wall portion 521 is arranged to extend along an outer circumferential surface of the magnet holding portion 514 of the hub body member 51.

[0049] The second top plate portion 522 is arranged to extend radially inward from an upper end portion of the outer wail portion 521 to assume the shape of a circular ring. The second top plate portion 522 is arranged in the recessed portion 515, which is defined in the upper surface of the first top plate portion 511 of the hub body member 51. In addition, the upper surface of the first top plate portion 511 and an upper surface of the second top plate portion 522 are arranged at the same axial position.

[0050] The flat plate holding portion 523 is arranged to extend radially outward from a lower end portion of the outer wall portion 521. The flat plate holding portion 523 is arranged to hold the air blowing portion 40 on a radially outer side of the magnet holding portion 514 of the hub body member 51. In the present preferred embodiment, the air blowing portion 40 is mounted on an upper surface of the flat plate holding portion 523. The flat plate holding portion 523 is thus arranged to hold a plurality of flat plates 410 included in the air blowing portion 40.

[0051] The bearing member 323 is a cylindrical member arranged to extend in the vertical direction with the central axis 9 as a center thereof. The bearing member 323 is arranged to extend along an outer circumferential surface of the first cylindrical portion 512 of the hub body member 51. In addition, the bearing member 323 is fixed to the outer circumferential surface of the first cylindrical portion 512. The cylindrical portion of the bearing housing 313 is arranged radially outside of the bearing member 323 and radially inside of the second cylindrical portion 513 of the hub body member 51.

[0052] The magnet 324 is fixed to the inner circumferential surface of the magnet holding portion 514 of the hub body member 51. In addition, the magnet 324 is arranged radially outside of the stator 312. The magnet 324 according to the present preferred embodiment is in the shape of a circular ring. A radially inner surface of the magnet 324 is arranged radially opposite to the stator 312 with a slight gap therebetween. In addition, an inner circumferential surface of the magnet 324 includes north and south poles arranged to alternate with each other in a circumferential direction. Note that a plurality of magnets may be used in place of the magnet 324 in the shape of a circular ring. In the case where the plurality of magnets are used, the magnets are arranged in the circumferential direction such that north and south poles of the magnets alternate with each other.

[0053] As illustrated in an enlarged view in FIG. 5, a lubricating fluid 300 is arranged between the bearing housing 313 and a combination of the shaft 321, the bearing member 32 3, and the hub body member 51. A polyolester oil or a diester oil, for example, is used as the lubricating fluid 300. The shaft 321, the hub 322, and the bearing member 323 are supported to be rotatable with respect to the bearing housing 313 through the lubricating fluid 300. Thus, in the present preferred embodiment, the bearing housing 313, which is a component of the stationary portion 31, the combination of the shaft 321, the bearing member 323, and the hub body member 51, each of which is a component of the rotating portion 32, and the lubricating fluid 300 together define a fluid dynamic bearing.

[0054] A surface of the lubricating fluid 300 is defined in a seal portion 301, which is a gap between an outer circumferential surface of the bearing housing 313 and an inner circumferential surface of the second cylindrical portion 513 of the hub body member 51. In the seal portion 301, the distance between the outer circumferential surface of the bearing housing 313 and the inner circumferential surface of the second cylindrical portion 513 is arranged to increase with decreasing height. In other words, in the seal portion 301, the distance between the outer circumferential surface of the bearing housing 313 and the inner circumferential surface of the second cylindrical portion 513 is arranged to increase with increasing distance from the surface of the lubricating fluid 300. Since the radial width of the seal portion 301 thus increases with decreasing height, the lubricating fluid 300 is attracted upward in the vicinity of the surface of the lubricating fluid 300. This reduces the likelihood that the lubricating fluid 300 will leak out of the seal portion 301.

[0055] Use of the fluid dynamic bearing as a bearing mechanism that connects the stationary portion 31 and the rotating portion 32 allows the rotating portion 32 to rotate stably. Thus, the likelihood of an occurrence of an unusual sound from the motor portion 30 can be reduced.

[0056] Once electric drive currents are supplied to the stator 312 in the motor portion 30 as described above, magnetic flux is generated around the stator 312. Then, interaction between the magnetic flux of the stator 312 and magnetic flux of the magnet 324 produces a circumferential torque between the stationary portion 31 and the rotating portion 32, so that the rotating portion 32 is caused to rotate about the central axis 9 with respect to the stationary portion 31. The air blowing portion 40, which is held by the flat plate holding portion 523 of the rotating portion 32, is caused to rotate about the central axis 9 together with the rotating portion 32.

[0057] Referring to FIGS. 4 and 5, the air blowing portion 40 includes the plurality of flat plates 410 and a plurality of spacers 420. The flat plates 410 and the spacers 420 are arranged to alternate with each other in the axial direction. In addition, adjacent ones of the flat plates 410 and the spacers 420 are fixed to each other through, for example, adhesion.

[0058] Referring to FIGS. 4 and 5, in the present preferred embodiment, the flat plates 410 include a top flat plate 411, which is arranged at the highest position, a bottom flat plate 412, which is arranged at the lowest position, and four intermediate flat plates 413, which are arranged below the top flat plate 411 and above the bottom flat plate 412. That is, the number of flat plates 410 included in the air blowing portion 40 according to the present preferred embodiment is six. The flat plates 410 are arranged in the axial direction with an axial gap 400 defined between adjacent ones of the flat plates 410.

[0059] Each flat plate 410 is made of, for example, a metal material, such as stainless steel, or a resin material. Each flat plate 410 may alternatively be made of, for example, paper. In this case, paper including a glass fiber, a metal wire, or the like in addition to plant fibers may be used. The flat plate 410 is able to achieve higher dimensional accuracy when the flat plate 410 is made of a metal material than when the flat plate 410 is made of a resin material.

[0060] In the present preferred embodiment, each of the top flat plate 411 and the four intermediate flat plates 413 is arranged to have the same shape and size. Referring to FIGS. 1, 2, and 5, each of the top flat plate 411 and the intermediate flat plates 413 includes an inner annular portion 61, an outer annular portion 62, a plurality of ribs 63, and a plurality of air holes 60. In the present preferred embodiment, the number of ribs 63 and the number of air holes 60 included in each of the top flat plate 411 and the intermediate flat plates 413 are both five. Each air hole 60 is arranged to be in communication with a space radially outside of the air blowing portion 40 through the axial gap(s) 400 adjacent to the flat plate 410 including the air hole 60 on the upper and/or lower sides of the flat plate 410. Each air hole 60 is arranged at a position overlapping with the air inlet 202 of the housing 20 when viewed in the axial direction.

[0061] The bottom flat plate 412 is an annular and plate-shaped member centered on the central axis 9. The bottom flat plate 412 has a central hole 65 arranged to pass therethrough in the vertical direction in a center thereof. The shape of each flat plate 410 will be described in detail below.

[0062] Referring to FIG. 4, each spacer 420 is a member in the shape of a circular ring. The spacers 420 are arranged between the flat plates 410 to secure the axial gaps 400 between the flat plates 410. Each spacer 420 has a central hole 429 arranged to pass therethrough in the vertical direction in a center thereof. The motor portion 30 is arranged in the central holes 65, which will be described below, of the flat plates 410 and the central holes 429 of the spacers 420.

[0063] Each spacer 420 is arranged at a position axially coinciding with the inner annular portion 61 of each of the top flat plate 411 and the intermediate flat plates 413. Thus, the spacer 420 is arranged in a region in the corresponding axial gap 400, the region covering only a portion of the radial extent of the corresponding axial gap 400.

[0064] Once the motor portion 30 is driven, the air blowing portion 40 is caused to rotate together with the rotating portion 32. As a result, viscous drag of a surface of each flat plate 410 and a centrifugal force together generate an air flow traveling radially outward in the vicinity of the surface of the flat plate 410. Thus, an air flow traveling radially outward is generated in each of the axial gaps 400 between the flat, plates 410. Thus, gas above the housing 20 is supplied to each axial gap 400 through the air inlet 202 of the housing 20 and the air holes 60 of the top flat plate 411 and the intermediate flat plates 413, and is discharged out of the blower apparatus 1 through the air outlet 201, which is defined in a side portion of the housing 20.

[0065] Here, each flat plate 410 is arranged to have an axial thickness of about 0.1 mm. Meanwhile, each axial gap 400 is arranged to have an axial dimension of about 0.3 mm. The axial dimension of the axial gap 400 is preferably in the range of 0.2 mm to 0.5 mm. An excessively large axial dimension of the axial gap 400 would lead to a separation between an air flow generated by a lower surface of the flat plate 410 on the upper side and an air flow generated by an upper surface of the flat plate 410 on the lower side during rotation of the air blowing portion 40. This separation could result in a failure to generate sufficient static pressure in the axial gap 400 to discharge a sufficient volume of air. Moreover, an excessively large axial dimension of the axial gap 400 would make it difficult to reduce the axial dimension of the blower apparatus 1. Accordingly, in this blower apparatus 1, the axial dimension of the axial gap 400 is arranged to be in the range of 0.2 mm to 0.5 mm. This arrangement allows the blower apparatus 1 to achieve a reduced thickness while allowing an increase in the static pressure in the axial gap 400 to discharge a sufficient volume of air.

[0066] In addition, referring to FIG. 2, the air inlet 202 is centered on the central axis 9. That is, a center of the air inlet 202 coincides with the central axis 9. Meanwhile, the air blowing portion 40 is also centered on the central axis 9. Accordingly, differences in pressure do not easily occur at different circumferential positions in the air blowing portion 40. This contributes to reducing noise. It is assumed that the term "coincide" as used here includes not only "completely coincide" but also "substantially coincide".

[0067] 1-2. Shapes of Flat Plates

[0068] Next, the shape of each flat plate 410 will now be described in detail below with reference to FIGS. 4 and 6. FIG. 6 is a top view of the flat plates 410.

[0069] Referring to FIG. 4, in the present preferred embodiment, each of the top flat, plate 411 and the four intermediate flat plates 413 is arranged to have the same shape and size. As described above, each of the top flat plate 411 and the intermediate flat plates 413 includes the inner annular portion 61, the outer annular portion 62, the plurality of ribs 63, and the plurality of air holes 60.

[0070] The inner annular portion 61 is an annular portion centered on the central axis 9. The inner annular portion 61 has the central hole 65 arranged to pass therethrough in the vertical direction in a center thereof. The outer annular portion 62 is an annular portion arranged radially outside of the inner annular portion 61 with the central axis 9 as a center thereof. Each rib 63 is arranged to join the inner annular portion 61 and the outer annular portion 62 to each other. Each air hole 60 is arranged to pass through the flat plate 410 in the axial direction. Each air hole 60 is surrounded by the inner annular portion 61, the outer annular portion 62, and two circumferentially adjacent ones of the ribs 63.

[0071] In a related-art blower apparatus that generates air flows by rotating an impeller including a plurality of blades, air flows generated by the impeller leak at upper and lower end portions of the impeller. This leakage of the air flows occurs regardless of the axial dimension of the blower apparatus. Therefore, as the blower apparatus is designed to be thinner, an effect of this leakage on the blower apparatus as a whole becomes greater, resulting in lower air blowing efficiency. Meanwhile, in the blower apparatus 1 according to the present preferred embodiment, the air flows are generated in the vicinity of the surfaces of the flat plates 410, and therefore, the air flows do not easily leak upward or downward. Therefore, even when the axial dimension of the air blowing portion 40, which generates the air flows, is reduced, a reduction in air blowing efficiency due to leakages of the air flows does not easily occur. That is, even when the blower apparatus 1 has a reduced thickness, a reduction in air blowing efficiency thereof does not easily occur.

[0072] In addition, in a blower apparatus including an impeller, periodic noise occurs owing to the shape, number, arrangement, and so on of blades. However, this blower apparatus 1 is superior to a comparable blower apparatus including an impeller in terms of being silent, because the air flows are generated by the viscous drag of the surface of each flat plate 410 and the centrifugal force in the blower apparatus 1.

[0073] In addition, from the viewpoint of P-Q characteristics (i.e., flow rate-static pressure characteristics), the blower apparatus 1 including the flat plates 410 is able to produce a higher static pressure in a low flow rate region than the blower apparatus including the impeller. Therefore, when compared to the blower apparatus including the impeller, the blower apparatus 1 is suitable for use in a densely packed case, from which only a relatively small volume of air can be discharged. Examples of such cases include cases of electronic devices, such as, for example, personal computers.

[0074] In the present preferred embodiment, the top flat plate 411 and all the intermediate flat plates 413 include the air holes 60. Accordingly, ail the axial gaps 400 are in axial communication with a space above the housing 20 through the air inlet 202 and the air holes 60.

[0075] Each of the top flat plate 411 and the intermediate flat plates 413 includes the air holes 60. Accordingly, in each of the top flat plate 411 and the intermediate flat plates 413, the outer annular portion 62, which is arranged radially outside of the air holes 60, defines an air blowing region which generates an air flow in the vicinity of a surface thereof. Meanwhile, the bottom flat plate 412 includes no air hole 60. Therefore, in an upper surface of the bottom flat plate 412, an entire region radially outside of a portion of the bottom flat plate 412 which makes contact with the spacer 420 defines an air blowing region. In other words, in the upper surface of the bottom flat plate 412, a region which axially coincides with the air holes 60 and the ribs 63 of the top flat plate 411 and the intermediate flat plates 413, and a region which axially coincides with the outer annular portions 62 thereof, together define the air blowing region. In addition, in a lower surface of the bottom flat plate 412, an entire region radially outside of a portion of the bottom flat plate 412 which makes contact with the flat plate holding portion 523 defines an air blowing region. Notice that an air flow is generated by a lower surface of the flat plate holding portion 523 as well.

[0076] As described above, the bottom flat plate 412 has air blowing regions wider than the air blowing regions of the top flat plate 411 and the intermediate flat plates 413. Therefore, the axial gap 400 between the lowest one of the intermediate flat plates 413 and the bottom flat plate 412 is able to have higher static pressure than any other axial gap 400.

[0077] Air flows passing downward through the air inlet 202 and the air holes 60 are drawn radially outward in each axial gap 400. Therefore, the air flows passing through the air holes 60 become weaker as they travel downward. In the present preferred embodiment, the bottom flat plate 412 is arranged to have an air blowing region wider than the air blowing regions of the top flat plate 411 and the intermediate flat plates 413 to cause a stronger air flow to be generated in the lowest one of the axial gaps 400 than in any other axial gap 400 to cause the air flows passing downward through the air holes 60 to be drawn toward the lowest axial gap 400. Thus, a sufficient volume of gas is supplied to the lowest axial gap 400 as well. As a result, the air blowing portion 40 achieves improved air blowing efficiency.

[0078] In this blower apparatus 1, each of the flat plates 410 includes a plurality of through holes 64 each of which is arranged to pass therethrough in the axial direction as illustrated in FIGS. 4 and 6. This leads to a reduction in weight of each flat plate 410. This in turn leads to a reduction in weight of the blower apparatus 1. In this blower apparatus 1, all the flat plates 410 include the through holes 64. Thus, all the flat plates 410 are reduced in weight. Accordingly, an additional reduction in the weight of the blower apparatus 1 as a whole can be achieved. In each of the top flat plate 411 and the intermediate flat plates 413, the through holes 64 are defined in the outer annular portion 62. That is, the through holes 64 are arranged radially outward of the air holes 60.

[0079] Each of the through holes 64 is circular in a plan view. Note that the through hole 64 may not necessarily be circular. For example, the through hole 64 may alternatively be elliptical, square, or rectangular in the plan view. Each through hole 64 is arranged to have an opening area smaller than an opening area of each air hole 60. Thus, unlike the air holes 60, each through hole 64 does not have a substantial effect of allowing an air flow to pass between a space above the flat plate 410 and a space below the flat plate 410. Therefore, the through hole 64 does not easily cause a reduction in the air blowing efficiency while reducing the weight of the flat plate 410.

[0080] In this blower apparatus 1, the flat plates 410 are arranged to rotate to one side in the circumferential direction along with rotation of the motor portion 30. Referring to FIG. 6, each of the ribs 63 is arranged to curve to an opposite side in the circumferential direction as the rib 63 extends radially outward. As a result, the rib 63 extends along a direction of an air flow that passes near a surface of the flat plate 410. This contributes to reducing the likelihood that a turbulent flow will occur near the rib 63, since the rib 63 does not easily disturb the air flow near the flat plate 410. This leads to an improvement in the air blowing efficiency of the blower apparatus 1. Note that each rib 63 may alternatively be arranged to extend in a straight line in a radial direction, or to extend in a straight line and to be inclined to the opposite side in the circumferential direction as it extends radially outward.

[0081] In each of the top flat plate 411 and the intermediate flat plates 413, each of the through holes 64 is arranged on a radially outer extension of a separate one of the ribs 63. No air hole 60 lies at a circumferential position at which any rib 63 lies, and therefore, in the outer annular portion 62, which defines the air blowing region, the radially outer extension of each rib 63 produces a relatively low air blowing efficiency, while a radially outer extension of each air hole 60 produces a higher air blowing efficiency. Therefore, if the through hole 64, which may cause a reduction in the air blowing efficiency, were arranged on the radially outer extension of each air hole 60, the air blowing efficiency might become lower than in the case where the through hole 64 is arranged on the radially outer extension of each rib 63. Accordingly, in this blower apparatus 1, the through hole 64 is arranged on the radially outer extension of each rib 63 to prevent the through hole 64 from causing a significant reduction in the air blowing efficiency.

2. EXAMPLE MODIFICATIONS

[0082] While a preferred embodiment of the present invention has been described above, it is to be understood that the present invention is not limited to the above-described preferred embodiment.

[0083] FIG. 7 is a top view of a plurality of flat plates 410A of a blower apparatus according to a modification of the above-described preferred embodiment. In the blower apparatus according to the modification illustrated in FIG. 7, each of the flat plates 410A includes a plurality of through holes 64A each of which is arranged to pass therethrough in the axial direction. The through holes 64A are arranged at the same radial position and at regular intervals in the circumferential direction. It is assumed here that the wording "regular intervals" includes "substantially regular intervals". That is, the through holes 64A are arranged at equal intervals in the circumferential direction. This allows each flat plate 410A to maintain an excellent weight balance in the circumferential direction. This in turn allows an air blowing portion including the flat plates 410A to stably rotate. As a result, a reduction in noise generated by the air blowing portion can be achieved.

[0084] FIG. 8 is a top view of a plurality of flat plates 410B of a blower apparatus according to another modification of the above-described preferred embodiment. In the blower apparatus according to the modification illustrated in FIG. 8, at least one of the flat plates 410B includes air holes 60B and an outer annular portion 62B, which is annular. The outer annular portion 62B defines an air blowing region arranged radially outside of the air holes 60B. In addition, each of the flat plates 410B includes a plurality of through holes 64B. The through holes 64B are arranged radially outward of a radial middle 620B of the outer annular portion 62B defining the air blowing region.

[0085] With the through holes 64B being defined in a radially outer portion of the outer annular portion 62B, weight balance of the flat plate 410B is shifted radially inward when compared to the case where the through holes 64B are not provided. This allows the flat plate 410B to stably rotate. This in turn leads to improved air blowing efficiency. In addition, vibration of an air blowing portion can be reduced to achieve a reduction in noise generated by the air blowing portion.

[0086] FIG. 9 is a top view of a plurality of flat plates 410C of a blower apparatus according to yet another modification of the above-described preferred embodiment. In the blower apparatus according to the modification illustrated in FIG. 9, at least one of the flat plates 410C includes air holes 60C and an outer annular portion 62C, which is annular. The outer annular portion 62C defines an air blowing region arranged radially outside of the air holes 60C. In addition, each of the flat plates 410C includes a plurality of through holes 64C. The through holes 64C are arranged radially inward of a radial middle 620C of the outer annular portion 62C defining the air blowing region. Thus, the through holes 64C may be defined in a radially inner portion of the outer annular portion 62C.

[0087] In the outer annular portion 62C, which defines the air blowing region, a portion radially outward of the radial middle 620C makes greater contributions to the volume of air to be discharged and air blowing efficiency than a portion radially inward of the radial middle 620C. Accordingly, the through holes 64C, which may cause a reduction in the air blowing efficiency, are arranged radially inward of the radial middle 620C to prevent a significant reduction in the volume of air to be discharged while reducing the weight of the flat plate 410C.

[0088] FIG. 10 is a top view of a plurality of flat plates 410D of a blower apparatus according to yet another modification of the above-described preferred embodiment. In the blower apparatus according to the modification illustrated in FIG. 10, each of the flat plates 410D includes a plurality of through holes 64D each of which is arranged to pass therethrough in the axial direction. The through holes 64D include a plurality of first through holes 641D and a plurality of second through holes 642D. Each first through hole 64ID is at a first distance D1 from a central axis 9D. In addition, each second through hole 642D is at a second distance D2 greater than the first distance D1 from the central axis 9D. Each of the first through holes 64ID is arranged at a circumferential position different from a circumferential position of each of the second through holes 642D.

[0089] Thus, the through holes 64B arranged at different radial positions do not radially overlap with each other. If a plurality of through holes radially overlapped with each other at a circumferential position, the flat plate would be reduced in rigidity at the circumferential position. In the modification illustrated in FIG. 10, the first through holes 641D and the second through holes 642D are arranged at different circumferential positions to limit a reduction in rigidity of the flat plate 410D.

[0090] FIG. 11 is a top view of a plurality of flat plates 410E of a blower apparatus according to yet another modification of the above-described preferred embodiment. In the blower apparatus according to the modification illustrated in FIG. 11, at least one of the flat plates 410E includes an inner annular portion 61E, which is annular, an outer annular portion 62E, which is annular, a plurality of ribs 63E, a plurality of air holes 60E, and a plurality of through holes 64E. The inner annular portion 61E is centered on a central axis 9E. The outer annular portion 62E is arranged radially outside of the inner annular portion 61E with the central axis 9E as a center thereof. Each of the ribs 63E is arranged to radially join the inner annular portion 61 and the outer annular portion 62 to each other. Each of the air holes 60E is surrounded by the inner annular portion 61E, the outer annular portion 62E, and two circumferentially adjacent ones of the ribs 63E, and is arranged to pass through the flat plate 410E in the axial direction. Each through hole 64E is arranged to pass through the flat plate 410E in the axial direction.

[0091] In the blower apparatus according to the modification illustrated in FIG. 11, the flat plates 410E are arranged to rotate to one side in the circumferential direction along with rotation of a motor portion. Each of the ribs 63E is arranged to curve to an opposite side in the circumferential direction as the rib 63E extends radially outward. As a result, the rib 63E extends along a direction of an air flow that passes near a surface of the flat plate 410E. This contributes to reducing the likelihood that a turbulent flow will occur near the rib 63E, since the rib 63E does not easily disturb the air flow near the flat plate 410E. This leads to an improvement in air blowing efficiency of the blower apparatus.

[0092] Each of the through holes 64E is arranged to curve to the opposite side in the circumferential direction as the through hole 64E extends radially outward. In addition, a line 640E (hereinafter referred to as a center line 640E) that joins circumferential middle points of each through hole 64E is arranged to curve to the opposite side in the circumferential direction as the line 640E extends radially outward. In addition, the center line 640E of each through hole 64E is arranged to extend radially outward with a curvature substantially equal to a curvature with which each rib 63E is arranged to extend radially outward. As a result, the through hole 64E extends along a direction of an air flow that passes near a surface of the flat plate 410E. This contributes to reducing the likelihood that a turbulent flow will occur near the through hole 64E, since the through hole 64E does not easily disturb the air flow near the flat plate 410E. This contributes to preventing the through hole 64E from causing a significant reduction in the air blowing efficiency of the blower apparatus. In addition, each of the through holes 64E is arranged on a radially outer extension of a separate one of the ribs 63E. This contributes to more effectively preventing the through hole 64E from causing a significant reduction in the air blowing efficiency.

[0093] FIG. 12 is a top view of a plurality of flat plates 410F of a blower apparatus according to yet another modification of the above-described preferred embodiment. In the blower apparatus according to the modification illustrated in FIG. 12, at least one of the flat plates 410F includes a plurality of ribs 63F, and a plurality of through holes 64F each of which is arranged to pass therethrough in the axial direction. Each through hole 64F is in the shape of a tear drop in a plan view. The through hole 64F is arranged to be symmetric with respect to a center line 640F thereof in the plan view. In the blower apparatus according to the modification illustrated in FIG. 12, the flat plates 410F are arranged to rotate to one side in the circumferential direction along with rotation of a motor portion. The center line 640F is arranged to extend in a straight line and to be inclined to an opposite side in the circumferential direction as it extends radially outward. Each through hole 64F is arranged with a pointed tip portion thereof on the radially inner side and a round base portion thereof on the radially outer side.

[0094] With the above arrangement, the through hole 64F extends along a direction of an air flow that passes near a surface of the flat plate 410F. This contributes to reducing the likelihood that a turbulent flow will occur near the through hole 64F, since the through hole 64F does not easily disturb the air flow near the flat plate 410F. This contributes to preventing the through hole 64F from causing a significant reduction in air blowing efficiency of the blower apparatus. In addition, each of the through holes 64F is arranged on a radially outer extension of a separate one of the ribs 63F. This contributes to more effectively preventing the through hole 64F from causing a significant reduction in the air blowing efficiency.

[0095] FIG. 13 is a top view of a plurality of flat plates 410G of a blower apparatus according to yet another modification of the above-described preferred embodiment. In the blower apparatus according to the modification illustrated in FIG. 13, at least one of the flat plates 410G includes a plurality of ribs 63G, and a plurality of through holes 64G each of which is arranged to pass therethrough in the axial direction. Each through hole 64G is in the shape of an airfoil in a plan view. In the blower apparatus according to the modification illustrated in FIG. 13, the flat plates 410G are arranged to rotate to one side in the circumferential direction along with rotation of a motor portion. Each through hole 64G is arranged with a leading edge thereof on the radially inner side and a trailing edge thereof on the radially outer side. A chord connecting the leading and trailing edges of the through hole 64G is arranged to slant to an opposite side in the circumferential direction as it extends radially outward.

[0096] With the above arrangement, the through hole 64G extends along a direction of an air flow that passes near a surface of the flat plate 410G. This contributes to reducing the likelihood that a turbulent flow will occur near the through hole 64G, since the through hole 64G does not easily disturb the air flow near the flat plate 410G. This contributes to preventing the through hole 64G from causing a significant reduction in air blowing efficiency of the blower apparatus. In addition, each of the through holes 64G is arranged on a radially outer extension of a separate one of the ribs 63G. This contributes to more effectively preventing the through hole 64G from causing a significant reduction in the air blowing efficiency.

[0097] FIG. 14 is a partial sectional view of a blower apparatus 1H according to yet another modification of the above-described preferred embodiment. In the blower apparatus 1H according to the modification illustrated in FIG. 14, a motor portion 30H includes a stationary portion 31H, a rotating portion 32H, and two ball bearings 33H.

[0098] The stationary portion 31H includes a stator fixing portion 311H and a stator 312H. The stator fixing portion 311H is a member being cylindrical and having a closed bottom and fixed to a housing 20H. The stator 312H is an armature fixed to an outer circumferential surface of the stator fixing portion 311H.

[0099] The rotating portion 32H includes a shaft 321H, a hub 322H, and a magnet 324H. At least a lower end portion of the shaft 321H is arranged inside of the stator fixing portion 311H. In addition, an upper end portion of the shaft 321H is fixed to the hub 322H. The magnet 324H is fixed to the hub 322H. The magnet 324H is arranged radially opposite to the stator 312H.

[0100] Each ball bearing 33H is arranged to connect the rotating portion 32H to the stationary portion 31H such that the rotating portion 32H is rotatable with respect to the stationary portion 31H. Specifically, an outer race of each ball bearing 33H is fixed to an inner circumferential surface of the stator fixing portion 311H of the stationary portion 31H. In addition, an inner race of each ball bearing 33H is fixed to an outer circumferential surface of the shaft 321H of the rotating portion 32H. Further, a plurality of balls, each of which is a spherical rolling element, are arranged between the outer race and the inner race. As described above, instead of a fluid dynamic bearing, rolling-element bearings, such as, for example, ball bearings, may be used as a bearing structure of the motor portion 30H.

[0101] In the modification illustrated in FIG. 14, the motor portion 30H includes the two ball bearings 33H. The ball bearings 33H are arranged near an upper end and a lower end of an axial range over which the inner circumferential surface of the stator fixing portion 311H and the shaft 321H are opposed to each other. This contributes to preventing the shaft 321H from being inclined with respect to a central axis 9H.

[0102] FIG. 15 is a top view of a blower apparatus 1J according to yet another modification of the above-described preferred embodiment. In the blower apparatus 1J according to the modification illustrated in FIG. 15, a housing 20J includes a plurality of air outlets 201J. Specifically, a side wall portion 22J includes the air outlets 201J, each of which is arranged to face in a radial direction, at a plurality of circumferential positions. The housing 20J includes tongue portions 203J, each of which is arranged near a separate one of the air outlets 201J. In addition, an air blowing portion 40J includes a plurality of flat plates 410J arranged in the axial direction with an axial gap defined between adjacent ones of the flat plates 410J.

[0103] In a centrifugal fan including an impeller, periodic noise occurs owing to the shape, number, arrangement, and so on of blades. In addition, such noise tends to easily occur around a tongue portion. Accordingly, when air is to be discharged in a plurality of directions, a deterioration in noise characteristics occurs because of an increased number of tongue portions. However, in this blower apparatus 1J, air flows traveling radially outward are generated by rotation of the flat plates 410J, and therefore, the blower apparatus 1J is able to achieve reduced periodic noise when compared to the centrifugal fan including the impeller. Therefore, the blower apparatus 1J, which is designed to discharge air in a plurality of directions, does not significantly deteriorate in noise characteristics due to the tongue portions 203J.

[0104] Note that, although the number of flat plates included in the air blowing portion is six in each of the above-described preferred embodiment and the modifications thereof, this is not essential to the present invention. The number of flat plates may alternatively be two, three, four, five, or more than six.

[0105] Also note that, although the hub is defined by two members, i.e., the hub body member and the flange member, in each of the above-described preferred embodiment and the modifications thereof, this is not essential to the present invention. The hub may alternatively be defined by a single member, or three or more members.

[0106] Also note that the detailed shape of any member may be different from the shape thereof as illustrated in the accompanying drawings of the present, application. For example, the shape of any of the housing, the air blowing portion, and the motor portion may be different from that according to each of the above-described preferred embodiment and the modifications thereof. Also note that features of the above-described preferred embodiment and the modifications thereof may be combined appropriately as long as no conflict arises.

[0107] Preferred embodiments of the present invention are applicable to blower apparatuses.

[0108] While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit, of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.

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