Patent Application
20130164158
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.
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.
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.
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
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
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.
Next, a second preferred embodiment of the present invention will now be described below.
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
The motor 10 is arranged to rotate the impeller 20 in accordance with drive currents. As illustrated in
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
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
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
As illustrated in
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
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.
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
Moreover, in the case of
Moreover, in the case of
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-279232 | Dec 2011 | JP | national |
