US20130164158A1

US20130164158A1 - Centrifugal fan

Info

Publication number: US20130164158A1
Application number: US13/611,510
Authority: US
Inventors: Naoki MATSUBA; Hiroyoshi Teshima; Kiyoto Ida
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2011-12-21
Filing date: 2012-09-12
Publication date: 2013-06-27
Also published as: CN103174660A; JP2013130094A; CN203035574U

Abstract

A side wall of a centrifugal fan includes a gap expanding portion arranged to gradually expand a gap between an impeller and the side wall from an upstream end toward a downstream end with respect to a rotation direction of a rotating portion. In the centrifugal fan, an electronic component arranging portion of a board is arranged in an area surrounded by the gap expanding portion, the impeller, and an air outlet, and accordingly does not overlap with a motor or the impeller in an axial direction. The electronic component arranging portion is arranged in an area extending, in a circumferential direction about a central axis, from a position 180 degrees upstream from a middle of the air outlet downstream to the middle of the air outlet, that is, in an area where a wind channel has a large width.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a centrifugal fan.
2. Description of the Related Art
Centrifugal fans used for internal cooling have often been installed in electronic devices, such as personal computers. Once such a centrifugal fan is driven, an air current is produced inside a case of the electronic device. This leads to a reduction in accumulation of heat inside the case. The structure of such a known centrifugal fan is described, for example, in JP-A 2001-135964.
Centrifugal fans include circuit boards arranged to supply drive currents to windings. Also, in many known centrifugal fans, a magnetic sensor arranged to detect the rotation rate of an impeller is mounted on the circuit board. Thus, in many known centrifugal fans, a circuit board having a variety of electronic components mounted thereon is disposed in the vicinity of a rotating portion of a motor or the impeller.
However, when the electronic components on the circuit board are arranged to overlap with the motor or the impeller in an axial direction, it is difficult to achieve a reduction in the axial dimension of the centrifugal fan. In particular, recent years have seen an increasing reduction in the thickness of notebook computers, tablet personal computers, and the like, and there has been an increasing demand for centrifugal fans installed in such electronic devices to decrease in thickness.
One conceivable way of meeting the above demand is, for example, to arrange a portion of the circuit board on which the electronic components are mounted in a wind channel on a radially outer side of the impeller. However, when the circuit board, or a portion thereof, is arranged in the wind channel, wind impinges on the circuit board, and this may cause an increase in wind noise of the centrifugal fan.

SUMMARY OF THE INVENTION

A centrifugal fan according to a preferred embodiment of the present invention includes a motor including a rotating portion, and arranged to rotate the rotating portion about a central axis extending in a vertical direction; an impeller arranged to rotate together with the rotating portion; a board arranged to supply a drive current to the motor; and a housing arranged to accommodate the rotating portion and the impeller, and including an upper air inlet and an air outlet. The housing includes a bottom plate arranged to spread substantially perpendicularly to the central axis on a lower side of the impeller; a top plate arranged to spread substantially perpendicularly to the central axis on an upper side of the impeller; and a side wall arranged to join an outer edge portion of the bottom plate and an outer edge portion of the top plate to each other on a radially outer side of the impeller. The side wall includes a gap expanding portion arranged to gradually expand a gap between the impeller and the side wall from an upstream end toward a downstream end with respect to a rotation direction of the rotating portion. A circumferential extent of the gap expanding portion is arranged to be at least half a circumferential extent of the entire side wall. The side wall includes a pair of edges arranged, respectively, on a downstream side and on an upstream side with respect to the rotation direction. An opening between the pair of edges is the air outlet. The top plate includes the upper air inlet over the motor. The board includes an electronic component arranging portion arranged to have one or more electronic components arranged thereon; a motor connection portion arranged to extend from the electronic component arranging portion toward the motor; and a draw-out portion arranged to extend from the electronic component arranging portion to an outside of the housing. The electronic component arranging portion is arranged in a predetermined area on the bottom plate. The predetermined area is an area surrounded by the gap expanding portion, the impeller, and the air outlet, and extending, in a circumferential direction about the central axis, from a position 180 degrees upstream from a middle of the air outlet downstream to the middle of the air outlet.
According to the above preferred embodiment of the present invention, the electronic component arranging portion is arranged radially outward of the impeller. Therefore, the electronic component arranging portion does not overlap with the motor or the impeller in an axial direction. This makes it possible to reduce the axial dimension of the centrifugal fan. In addition, the electronic component arranging portion is arranged in an area where a wind channel has a large width. This contributes to reducing wind noise caused by the electronic component arranging portion.
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

FIG. 1 is a horizontal cross-sectional view of a centrifugal fan according to a first preferred embodiment of the present invention.

FIG. 2 is a top view of a centrifugal fan according to a second preferred embodiment of the present invention.

FIG. 3 is a bottom view of the centrifugal fan according to the second preferred embodiment.

FIG. 4 is a horizontal cross-sectional view of the centrifugal fan according to the second preferred embodiment.

FIG. 5 is a vertical cross-sectional view of the centrifugal fan according to the second preferred embodiment.

FIG. 6 is a horizontal cross-sectional view of a centrifugal fan according to a modification of the second preferred embodiment.

FIG. 7 is a horizontal cross-sectional view of a centrifugal fan according to another modification of the second preferred embodiment.

FIG. 8 is a horizontal cross-sectional view of a centrifugal fan according to yet another modification of the second preferred embodiment.

FIG. 9 is a top view of a centrifugal fan according to yet another modification of the second preferred embodiment.

FIG. 10 is a horizontal cross-sectional view of a centrifugal fan according to yet another modification of the second preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. It is assumed herein that a direction parallel to a central axis of a motor is referred to by the term “axial direction”, “axial”, or “axially”, that directions perpendicular to the central axis of the motor are referred to by the term “radial direction”, “radial”, or “radially”, and that a circumferential direction about the central axis of the motor is referred to by the term “circumferential direction”, “circumferential”, or “circumferentially”. It is also assumed herein that a vertical direction is the axial direction, and that a side on which a top plate of a housing is arranged with respect to a bottom plate of the housing is defined as an upper side. The shape of each member or portion and relative positions of different members or portions will be described based on the above assumptions. It should be noted, however, that the above definitions of the vertical direction and the upper and lower sides are simply made for the sake of convenience in description, and should not be construed to restrict in any way the orientation of a centrifugal fan according to any embodiment of the present invention when in use.

1. First Preferred Embodiment

FIG. 1 is a horizontal cross-sectional view of a centrifugal fan 1A according to a first preferred embodiment of the present invention. As illustrated in FIG. 1, the centrifugal fan 1A includes a motor 10A, an impeller 20A, a housing 30A, and a board 40A.
The motor 10A includes a stationary portion fixed to the housing 30A, and a rotating portion 60A supported to be rotatable with respect to the stationary portion. The motor 10A is arranged to rotate the rotating portion 60A about a central axis 9A extending in a vertical direction. The impeller 20A is arranged to rotate together with the rotating portion 60A. The housing 30A is arranged to accommodate the rotating portion 60A and the impeller 20A, and includes an upper air inlet 321A and an air outlet 333A. The board 40A is arranged to supply drive currents to the motor 10A.
The housing 30A includes a bottom plate 31A, a top plate, and a side wall 33A. The bottom plate 31A is arranged to spread substantially perpendicularly to the central axis 9A on a lower side of the impeller 20A. The top plate is arranged to spread substantially perpendicularly to the central axis 9A on an upper side of the impeller 20A. The side wall 33A is arranged to join an outer edge portion of the bottom plate 31A and an outer edge portion of the top plate to each other on a radially outer side of the impeller 20A. The side wall 33A includes a gap expanding portion 334A arranged to gradually expand a gap between the impeller 20A and the side wall 33A from an upstream end toward a downstream end with respect to a rotation direction of the rotating portion 60A. The circumferential extent of the gap expanding portion 334A is arranged to be at least half the circumferential extent of the entire side wall 33A.
The top plate includes the aforementioned upper air inlet 321A over the motor 10A, as indicated by a chain double-dashed line in FIG. 1. The side wall 33A includes a pair of edges 331A and 332A arranged, respectively, on a downstream side and on an upstream side with respect to a rotation direction of the motor 10A. An opening between the pair of edges 331A and 332A is the aforementioned air outlet 333A.
The board 40A includes an electronic component arranging portion 41A, a motor connection portion 42A, and a draw-out portion 43A. An electronic component 411A is arranged on the electronic component arranging portion 41A. The motor connection portion 42A is arranged to extend from the electronic component arranging portion 41A toward the motor 10A. The draw-out portion 43A is arranged to extend from the electronic component arranging portion 41A to an outside of the housing 30A.
The electronic component arranging portion 41A of the board 40A is arranged in an area 70A on the bottom plate 31A, the area 70A being represented by a broken line in FIG. 1. The area 70A is surrounded by the gap expanding portion 334A, the impeller 20A, and the air outlet 333A. When the electronic component arranging portion 41A is arranged radially outward of the impeller 20A as described above, the electronic component arranging portion 41A does not overlap with the motor 10A or the impeller 20A in the axial direction. This makes it possible to reduce the axial dimension of the centrifugal fan 1A.
The area 70A is an area which extends, in a circumferential direction about the central axis 9A, from a position 180 degrees upstream from a middle of the air outlet 333A downstream to the middle of the air outlet 333A. The electronic component arranging portion 41A is therefore arranged in an area where a wind channel has a large width. This contributes to reducing wind noise caused by the electronic component arranging portion 41A.

2. Second Preferred Embodiment

Next, a second preferred embodiment of the present invention will now be described below. FIG. 2 is a top view of a centrifugal fan 1 according to the second preferred embodiment. FIG. 3 is a bottom view of the centrifugal fan 1. FIG. 4 is a horizontal cross-sectional view of the centrifugal fan 1. FIG. 5 is a vertical cross-sectional view of the centrifugal fan 1 taken along line A-A in FIGS. 2 to 4.
The centrifugal fan 1 is installed in an electronic device, such as a notebook computer, and is used to cool an inside of the electronic device. As illustrated in FIGS. 2 to 5, the centrifugal fan 1 according to the present preferred embodiment includes a motor 10, an impeller 20, a housing 30, and a board 40.
The motor 10 is arranged to rotate the impeller 20 in accordance with drive currents. As illustrated in FIG. 5, the motor 10 includes a stationary portion 50 fixed to the housing 30, and a rotating portion 60 supported to be rotatable with respect to the stationary portion 50. The motor 10 is arranged to rotate the rotating portion 60 about a central axis 9. The impeller 20 is arranged to rotate together with the rotating portion 60. The stationary portion 50 includes a joining member 51, a stator core 52, windings 53, a sleeve 54, and a cap 55. The rotating portion 60 includes a shaft 61, a rotor holder 62, and a plurality of magnets 63.
The joining member 51 is fixed to a bottom plate 31 of the housing 30. Each of the stator core 52 and the sleeve 54 is supported by the joining member 51. The stator core 52 includes a plurality of teeth 521 arranged to extend radially with respect to the central axis 9. Each of the windings 53 is defined by a conducting wire wound around a separate one of the teeth 521. The sleeve 54 is a substantially cylindrical member fixed to an inner circumferential surface of the joining member 51. The cap 55 is arranged to close a lower opening of the sleeve 54.
The shaft 61 is a columnar member arranged to extend in an axial direction. The shaft 61 is inserted inside the sleeve 54. The rotor holder 62 includes an inner cylindrical portion 621, a plate portion 622, and an outer cylindrical portion 623. The inner cylindrical portion 621 is arranged to surround an outer circumferential surface of the shaft 61. In addition, the inner cylindrical portion 621 is arranged to extend downward from the plate portion 662. The plate portion 622 is arranged to extend radially outward from an upper end portion of the shaft 61. The outer cylindrical portion 623 is arranged to extend downward from an outer edge portion of the plate portion 622. The magnets 63 are fixed to an inner circumferential surface of the outer cylindrical portion 623 on a radially outer side of the stator core 52. In addition, the magnets 63 are arranged in a circumferential direction such that north and south poles alternate with each other. Although the plurality of magnets 63 are arranged in the circumferential direction in the present preferred embodiment, a ring-shaped magnet in which north and south poles are arranged alternately in the circumferential direction may be used in other preferred embodiments of the present invention.
A lubricating fluid 11 is arranged between a combination of the sleeve 54 and the cap 55 of the stationary portion 50 and a combination of the inner cylindrical portion 621 and the shaft 61 of the rotating portion 60. In the motor 10, the sleeve 54, the cap 55, the shaft 61, and the inner cylindrical portion 621 are arranged to together define a fluid dynamic bearing arranged to allow the stationary portion 50 and the rotating portion 60 to rotate relative to each other through the lubricating fluid 11. A polyolester oil or a diester oil is used as the lubricating fluid 11, for example.
Once the drive currents are supplied to the windings 53 through the board 40, magnetic flux is generated around each of the teeth 521 of the stator core 52. Then, a circumferential torque is produced by interaction between the magnetic flux of the teeth 521 and that of the magnets 63, so that the rotating portion 60 is caused to rotate about the central axis 9 with respect to the stationary portion 50.
The impeller 20 includes an annular impeller base portion 21 and a plurality of blades 22. The impeller base portion 21 is fixed to the rotating portion 60. Specifically, the impeller base portion 21 is fixed to an outer circumferential surface of the outer cylindrical portion 623 of the rotor holder 62. The blades 22 are arranged at regular intervals in the circumferential direction as represented by chain double-dashed lines in FIG. 4. Each of the blades 22 is arranged to extend radially outward from the impeller base portion 21. The impeller base portion 21 and the blades 22 are defined as a single resin member by, for example, an injection molding process. Note, however, that the impeller base portion 21 and the blades 22 may be defined by separate members. The impeller base portion 21 and the blades 22 are arranged to rotate about the central axis 9 together with the rotating portion 60 of the motor 10.
The housing 30 includes the bottom plate 31, a top plate 32, and a side wall 33. The bottom plate 31 is arranged to spread substantially perpendicularly to the central axis 9 on a lower side of the impeller 20. The top plate 32 is arranged to spread substantially perpendicularly to the central axis 9 on an upper side of the impeller 20. The side wall 33 is arranged to partially join an outer edge portion of the bottom plate 31 and an outer edge portion of the top plate 32 to each other on a radially outer side of the impeller 20. The impeller 20 and the rotating portion 60 of the motor 10 are accommodated in an interior space of the housing 30, which is surrounded by the bottom plate 31, the top plate 32, and the side wall 33.
As illustrated in FIGS. 2 and 5, the top plate 32 includes an upper air inlet 321 arranged to extend in the vertical direction therethrough. The upper air inlet 321 is arranged over the motor 10. In addition, the upper air inlet 321 is arranged in the shape of a circle centered on the central axis 9 in a plan view. The side wall 33 includes a pair of edges 331 and 332 arranged, respectively, on a downstream side and on an upstream side with respect to a rotation direction of the impeller 20. An opening as an air outlet 333 is defined between the pair of edges 331 and 332.
Once the impeller 20 is rotated, a gas is drawn into the housing 30 through the upper air inlet 321. The gas drawn into the housing 30 receives a centrifugal force caused by the impeller 20, and is caused to flow in the circumferential direction in a wind channel 34 defined between the impeller 20 and the side wall 33, as indicated by an arrow in FIG. 4. The gas is then caused to travel from the wind channel 34 to the air outlet 333, and be discharged out of the housing 30 through the air outlet 333.
As illustrated in FIG. 4, the radial width of the wind channel 34 defined between the side wall 33 and the impeller 20 is arranged to gradually increase from an upstream end toward a downstream end with respect to a rotation direction of the rotating portion 60. In other words, the side wall 33 includes a gap expanding portion 334 arranged to gradually expand a radial gap between the impeller 20 and the side wall 33 from an upstream end toward a downstream end with respect to the rotation direction. The circumferential extent of the gap expanding portion 334 is arranged to be at least half the circumferential extent of the entire side wall 33.
An electronic circuit configured to supply the drive currents to the motor 10 is mounted on the board 40. The board 40 according to the present preferred embodiment is a flexible printed circuit board. The board 40 includes an electronic component arranging portion 41, a motor connection portion 42, and a draw-out portion 43. Each of the electronic component arranging portion 41 and the motor connection portion 42 is fixed to an upper surface of the bottom plate 31 of the housing 30. One or more electronic components 411 are arranged on the electronic component arranging portion 41. The electronic component arranging portion 41 accordingly includes a portion that has an increased axial height because of the electronic component(s) 411.
The motor connection portion 42 is arranged to extend from the electronic component arranging portion 41 toward the motor 10. Four land portions 421 are each arranged in the vicinity of an end portion of the motor connection portion 42 on a side near the motor 10. In the present preferred embodiment, the four land portions 421 are used for a U phase, a V phase, a W phase, and common, respectively. End portions of the windings 53 of the motor 10 are connected to the land portions 421 through a solder.
The draw-out portion 43 is arranged to extend from the electronic component arranging portion 41 to an outside of the housing 30. In the present preferred embodiment, the draw-out portion 43 is arranged to first extend radially inward from the electronic component arranging portion 41, and then be drawn out of the housing 30 through a draw-out opening 311 defined in the bottom plate 31 of the housing 30. The housing 30 according to the present preferred embodiment includes the draw-out opening 311 separately from the upper air inlet 321 and the air outlet 333. A connector is arranged at a top end of the draw-out portion 43. The connector is connected to a power supply unit.
The electronic component arranging portion 41 is arranged in the wind channel 34. Therefore, a wind blowing in the wind channel 34 can be used to cool the electronic component(s) 411 on the electronic component arranging portion 41. The board 40 according to the present preferred embodiment has mounted thereon a so-called sensorless drive circuit, which does not include a magnetic sensor arranged to detect the rotation rate of the rotating portion 60. It is therefore possible to arrange the electronic component arranging portion 41 of the board 40 at a position away from the magnets 63 of the motor 10.
The electronic component arranging portion 41 is arranged in an area surrounded by a radially outer end portion of the impeller 20, an inner circumferential surface of the gap expanding portion 334 of the side wall 33, and the air outlet 333. That is, the electronic component arranging portion 41 is arranged radially outward of the impeller 20. When the electronic component arranging portion 41 is arranged as described above, the electronic component arranging portion 41 does not overlap with the motor 10 or the impeller 20 in the axial direction. This makes it possible to reduce the axial dimension of the centrifugal fan 1.
In particular, the board 40 according to the present preferred embodiment is a flexible printed circuit board. The board 40 itself therefore has a reduced axial dimension compared to a rigid board, such as a glass epoxy board. This leads to an additional reduction in the axial dimension of the centrifugal fan 1.
If the electronic component arranging portion were arranged in an area where the wind channel has a small width or in the vicinity of the impeller, wind noise caused by the electronic component arranging portion would be louder. In view of this consideration, the electronic component arranging portion 41 is arranged in the vicinity of the edge 331 of the side wall 33 on the downstream side with respect to the rotation direction in the present preferred embodiment. More specifically, the electronic component arranging portion 41 is arranged near and along both the side wall 33 and the air outlet 333. In this manner, the electronic component arranging portion 41 is arranged far away from the impeller 20. A reduction in the wind noise caused by the electronic component arranging portion 41 is thereby achieved.
In order to reduce the wind noise caused by the electronic component arranging portion 41, it is desirable that the electronic component arranging portion 41 should be arranged in an area where the wind channel 34 has a large radial width. It is preferable, for example, that the electronic component arranging portion 41 should be arranged in an area which extends, in the circumferential direction about the central axis 9, from a position 180 degrees upstream from a middle of the air outlet 333 downstream to the middle of the air outlet 333. Moreover, a further reduction in the wind noise caused by the electronic component arranging portion 41 is achieved when the electronic component arranging portion 41 is arranged in an area which extends, in the circumferential direction about the central axis 9, from a position 90 degrees upstream from the middle of the air outlet 333 downstream to the middle of the air outlet 333.
Furthermore, in the present preferred embodiment, the electronic component arranging portion 41 is arranged such that the distance between the electronic component arranging portion 41 and the side wall 33 is smaller than the distance between the electronic component arranging portion 41 and the impeller 20. The electronic component arranging portion 41 can thus be arranged far away from the impeller 20. A further reduction in the wind noise caused by the electronic component arranging portion 41 is thereby achieved.
As illustrated in FIG. 4, in the present preferred embodiment, the draw-out opening 311 of the bottom plate 31 is arranged radially inward of the radially outer end portion of the impeller 20 in a plan view. The draw-out opening 311 is thus arranged not to face the wind channel 34. This contributes to reducing the likelihood of a leakage of a gas flowing in the wind channel 34 through the draw-out opening 311. This in turn contributes to increasing static pressure of the centrifugal fan 1. Note that the draw-out opening 311 may be arranged radially inward of a radially outer edge portion of the impeller base portion 21 in a plan view in order to achieve a further reduction in the likelihood of the leakage of the gas through the draw-out opening 311.
In the present preferred embodiment, at least one of the land portions 421 is arranged in the area which extends, in the circumferential direction about the central axis 9, from the position 180 degrees upstream from the middle of the air outlet 333 downstream to the middle of the air outlet 333. This leads to a decreased wiring distance between the electronic component(s) 411 on the electronic component arranging portion 41 and the land portions 421 of the motor connection portion 42. The decreased wiring distance leads to reduced electrical noise between the electronic component arranging portion 41 and the windings 53.
Moreover, in the present preferred embodiment, wires which connect the electronic component(s) 411 and the land portions 421 to each other are each arranged to extend without bending at an acute angle. The wiring distance between the electronic component(s) 411 and the land portions 421 is thereby further decreased. This leads to a further reduction in the electrical noise between the electronic component arranging portion 41 and the windings 53.
In particular, the board 40 according to the present preferred embodiment has the sensorless drive circuit mounted thereon. The sensorless drive circuit controls the drive currents based on slight induced voltages generated in the windings 53. Therefore, the electrical noise tends to easily affect the control of drive of the motor 10. However, a layout of the board 40 according to the present preferred embodiment achieves a reduction in the electrical noise between the electronic component arranging portion 41 and the windings 53 as described above, which enables the sensorless drive circuit to perform the drive control with increased accuracy.

3. Example Modifications

While preferred embodiments of the present invention have been described above, it is to be understood that the present invention is not limited to the above-described preferred embodiments.
The draw-out opening may be arranged radially outward of the radially outer end portion of the impeller in a plan view. This makes it possible to decrease the distance between the electronic component arranging portion and the draw-out opening as compared to the case of the above-described second preferred embodiment. This makes it possible to reduce the length of the draw-out portion.
For example, as is the case with a centrifugal fan 1B according to a modification of the second preferred embodiment illustrated in FIG. 6, a draw-out opening 335B may be defined in a side wall 33B of a housing 30B. In the case of FIG. 6, a draw-out portion 43B of a board 40B is arranged to directly extend radially outward from an electronic component arranging portion 41B to the draw-out opening 335B without extending radially inward. As a result, the length of the draw-out portion 43B is shorter than that of the draw-out portion 43 according to the second preferred embodiment. A shorter length of the draw-out portion 43B leads to a reduction in electrical noise introduced between the power supply unit and the electronic component arranging portion 41B.
FIG. 7 is a horizontal cross-sectional view of a centrifugal fan 1C according to another modification of the second preferred embodiment. In the case of FIG. 7, a bottom plate 31C of a housing 30C includes a plurality of lower air inlets 312C. Each lower air inlet 312C is a through hole arranged under a rotating portion 60C of a motor or under an impeller 20C. In this case, a gas can be introduced into the housing 30C through both an upper air inlet and the lower air inlets 312C.
Moreover, in the case of FIG. 7, a draw-out portion 43C of a board 40C is arranged to be drawn out of the housing 30C through one of the lower air inlets 312C. When the lower air inlets 312C are used to draw out the draw-out portion 43C, it is not necessary to provide an opening dedicated to the draw-out portion 43C.
FIG. 8 is a horizontal cross-sectional view of a centrifugal fan 1D according to yet another modification of the second preferred embodiment. In the case of FIG. 8, a draw-out opening 335D is arranged at a position on an opposite side of a motor with respect to an electronic component arranging portion 41D. In addition, a bottom plate 31D of a housing 30D includes a plurality of lower air inlets 312D. Each lower air inlet 312D is a through hole arranged under a rotating portion 60D of the motor or under an impeller 20D.
Moreover, in the case of FIG. 8, a draw-out portion 43D of a board 40D is arranged to extend to the draw-out opening 335D along ribs 313D each arranged between adjacent ones of the lower air inlets 312D. This allows the draw-out portion 43D to extend from the electronic component arranging portion 41D to the draw-out opening 335D without preventing gas introduction through the lower air inlets 312D.
FIG. 9 is a top view of a centrifugal fan 1E according to yet another modification of the second preferred embodiment. In the case of FIG. 9, a draw-out portion 43E of a board 40E is arranged to be drawn out of a housing 30E through an air outlet 333E. After being drawn out through the air outlet 333E, the draw-out portion 43E is bent upward to extend above an upper surface of a top plate 32E and extend sideways. When the air outlet 333E is used to draw out the draw-out portion 43E as described above, the housing 30E does not need to include an opening dedicated to the draw-out portion. Therefore, both a reduction in rigidity of the housing 30E and the likelihood of a leakage of the gas out of the housing 30E can be reduced. Note that, after being drawn out through the air outlet 333E, the draw-out portion 43E may be bent downward to extend below a lower surface of a bottom plate and extend sideways.
FIG. 10 is a horizontal cross-sectional view of a centrifugal fan 1F according to yet another modification of the second preferred embodiment. In the case of FIG. 10, an upper surface of an electronic component arranging portion 41F of a board 40F is covered with a potting portion 44F made of a resin. In this case, electronic components 411F on the electronic component arranging portion 41F are protected from an air current while the electronic component arranging portion 41F is arranged in a wind channel 34F.
Centrifugal fans according to other preferred embodiments of the present invention may differ in details of structure from the centrifugal fans according to the above-described preferred embodiments and the modifications thereof. For example, the number of land portions arranged in the motor connection portion of the board may be one, two, three, or more than four. Also, the side wall and one of the bottom plate and the top plate of the housing may be defined by a single member.
Also, the board may be a rigid board, such as a glass epoxy board. In the case where the rigid board is used, the draw-out portion may be a conducting wire. Also, a fluid dynamic bearing mechanism may be used as a bearing portion of the motor as in the above-described second preferred embodiment, or alternatively, a bearing mechanism of another type, such as a plain bearing, may be used.
Also, centrifugal fans according to other preferred embodiments of the present invention may be installed in devices other than electronic devices. Also, centrifugal fans according to other preferred embodiments of the present invention may be used for purposes other than cooling. Note, however, that the present invention is particularly useful for centrifugal fans used in notebook PCs or tablet PCs, since a reduction in thickness is particularly demanded of the notebook PCs and the tablet PCs.
Also note that features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises.
The present invention is applicable to centrifugal fans.

Claims

What is claimed is:

1. A centrifugal fan comprising:

a motor including a rotating portion, and arranged to rotate the rotating portion about a central axis extending in a vertical direction;

an impeller arranged to rotate together with the rotating portion;

a board arranged to supply a drive current to the motor; and

a housing arranged to accommodate the rotating portion and the impeller, and including an upper air inlet and an air outlet; wherein

the housing includes:

a bottom plate arranged to spread substantially perpendicularly to the central axis on a lower side of the impeller;

a top plate arranged to spread substantially perpendicularly to the central axis on an upper side of the impeller; and

a side wall arranged to join an outer edge portion of the bottom plate and an outer edge portion of the top plate to each other on a radially outer side of the impeller;

the side wall includes a gap expanding portion arranged to gradually expand a gap between the impeller and the side wall from an upstream end toward a downstream end with respect to a rotation direction of the rotating portion;

a circumferential extent of the gap expanding portion is arranged to be at least half a circumferential extent of the entire side wall;

the side wall includes a pair of edges arranged, respectively, on a downstream side and on an upstream side with respect to the rotation direction;

an opening between the pair of edges is the air outlet;

the top plate includes the upper air inlet over the motor;

the board includes:

an electronic component arranging portion arranged to have one or more electronic components arranged thereon;

a motor connection portion arranged to extend from the electronic component arranging portion toward the motor; and

a draw-out portion arranged to extend from the electronic component arranging portion to an outside of the housing;

the electronic component arranging portion is arranged in a predetermined area on the bottom plate; and

the predetermined area is an area surrounded by the gap expanding portion, the impeller, and the air outlet, and extending, in a circumferential direction about the central axis, from a position 180 degrees upstream from a middle of the air outlet downstream to the middle of the air outlet.

2. The centrifugal fan according to claim 1, wherein the board is a flexible printed circuit board.

3. The centrifugal fan according to claim 1, wherein a distance between the electronic component arranging portion and the side wall is arranged to be smaller than a distance between the electronic component arranging portion and the impeller.

4. The centrifugal fan according to claim 2, wherein a distance between the electronic component arranging portion and the side wall is arranged to be smaller than a distance between the electronic component arranging portion and the impeller.

5. The centrifugal fan according to claim 3, wherein the electronic component arranging portion is arranged in a vicinity of the edge of the side wall on the downstream side with respect to the rotation direction.

6. The centrifugal fan according to claim 4, wherein the electronic component arranging portion is arranged in a vicinity of the edge of the side wall on the downstream side with respect to the rotation direction.

7. The centrifugal fan according to claim 1, wherein the housing includes, separately from the upper air inlet and the air outlet, a draw-out opening through which the draw-out portion is arranged to be drawn out of the housing.

8. The centrifugal fan according to claim 7, wherein the draw-out opening is arranged radially inward of a radially outer end portion of the impeller in a plan view.

9. The centrifugal fan according to claim 7, wherein the draw-out opening is arranged radially outward of a radially outer end portion of the impeller in a plan view.

10. The centrifugal fan according to claim 9, wherein the draw-out opening is defined in the side wall.

11. The centrifugal fan according to claim 7, wherein

the impeller includes an annular impeller base portion fixed to the rotating portion, and a plurality of blades arranged to extend radially outward from the impeller base portion; and

the draw-out opening is arranged radially inward of a radially outer edge portion of the impeller base portion in a plan view.

12. The centrifugal fan according to claim 1, wherein the electronic component arranging portion is arranged in an area extending, in the circumferential direction about the central axis, from a position 90 degrees upstream from the middle of the air outlet downstream to the middle of the air outlet.

13. The centrifugal fan according to claim 1, wherein

the bottom plate includes a lower air inlet arranged under the motor or the impeller; and

the draw-out portion is arranged to be drawn out of the housing through the lower air inlet.

14. The centrifugal fan according to claim 1, wherein

the bottom plate includes a plurality of lower air inlets each of which is arranged under the motor or the impeller, and a rib arranged between adjacent ones of the lower air inlets; and

the draw-out portion is arranged to extend along the rib.

15. The centrifugal fan according to claim 1, wherein the draw-out portion is arranged to be drawn out of the housing through the air outlet.

16. The centrifugal fan according to claim 1, wherein

the motor connection portion includes land portions to which windings of the motor are connected; and

at least one of the land portions is arranged in an area extending, in the circumferential direction about the central axis, from the position 180 degrees upstream from the middle of the air outlet downstream to the middle of the air outlet.

17. The centrifugal fan according to claim 16, wherein wires connecting the one or more electronic components on the electronic component arranging portion and the land portions to each other are each arranged to extend without bending at an acute angle.

18. The centrifugal fan according to claim 1, further comprising a potting portion made of a resin, and arranged to cover the electronic component arranging portion.