Patent Application
20140072423
1. Field of the Invention
The present invention relates to a centrifugal fan.
2. Description of the Related Art
Small and high-performance electronic devices, such as notebook PCs, produce a large amount of heat at CPUs and the like inside chassis thereof. This makes it important to take measures against the heat. One common measure against the heat is to install blower fans inside the chassis to discharge the heat. Meanwhile, there has been a demand for a reduction in thickness of the notebook PCs. Accordingly, the blower fans have been required to be reduced in thickness while reducing a deterioration in air-blowing performance.
In the case where a centrifugal fan is used as such a blower fan, members each of which is made of a metal or a resin and is in the shape of a thin plate are combined together to define a housing in order to fulfill the above requirement. A fan casing described in JP-A 2008-157216, for example, is made up of a frame and a cover. The frame includes a bottom portion and a side wall portion, and is molded by die casting using a resin or an aluminum alloy. The cover is made of a resin or a metal, and is defined in the shape of a plate. The cover is fixed on the frame.
In the case where the plate in the shape of a board is attached to the side wall portion, a right-angled corner portion is defined between the side wall portion and the plate inside the housing. An air sent radially outward from an impeller stays in the corner portion. This results in a decrease in efficiency with which an air is sent out through an air outlet. Moreover, since an air current is disturbed at the corner portion, the corner portion becomes a cause for noise as well.
A centrifugal fan according to a preferred embodiment of the present invention includes an impeller centered on a central axis extending in a vertical direction; a motor portion arranged to rotate the impeller about the central axis; and a housing arranged to accommodate the impeller. The housing includes an upper plate portion arranged to cover an upper side of the impeller; a lower plate portion arranged to cover a lower side of the impeller, and arranged to have the motor portion fixed thereto; and a side wall portion arranged to cover a side of the impeller, and arranged to define an air outlet together with the upper and lower plate portions. At least one of the upper and lower plate portions includes an air inlet. The upper plate portion, the side wall portion, and the lower plate portion are arranged to together define an air channel portion arranged to surround the impeller. A boundary between an inside surface of the side wall portion and one of a lower surface of the upper plate portion and an upper surface of the lower plate portion is arranged to have a flow control member arranged thereon, the flow control member extending in a line along the boundary. The flow control member includes a flow control surface arranged to extend radially outward from the one of the lower surface of the upper plate portion and the upper surface of the lower plate portion to the inside surface of the side wall portion while becoming more distant from the one of the lower surface of the upper plate portion and the upper surface of the lower plate portion.
The centrifugal fan according to the above preferred embodiment of the present invention is able to achieve an improvement in air blowing efficiency.
It is assumed herein that an upper side and a lower side in a direction parallel to a central axis a centrifugal fan illustrated in
The centrifugal fan 1 includes a motor portion 2, a housing 3, and an impeller 4. The impeller 4 is centered on a central axis J1 extending in the vertical direction. The motor portion 2 is arranged to rotate the impeller 4 about the central axis J1. The housing 3 is arranged to accommodate the motor portion 2 and the impeller 4.
The housing 3 includes an upper plate portion 31, a lower plate portion 32, and a side wall portion 33. The upper plate portion 31 is arranged to cover an upper side of the impeller 4. The lower plate portion 32 is arranged to cover a lower side of the impeller 4. The motor portion 2 is fixed to the lower plate portion 32. The side wall portion 33 is arranged to cover a side of the impeller 4. The side wall portion 33 is arranged to define an air outlet 331 together with the upper and lower plate portions 31 and 32. The upper plate portion 31, the side wall portion 33, and the lower plate portion 32 are arranged to together define an air channel portion 30 arranged to surround the impeller 4.
Each of the upper and lower plate portions 31 and 32 is made of a metal, such as an aluminum alloy or stainless steel, and is defined in the shape of a thin plate. The side wall portion 33 is made of an aluminum alloy, and is molded by die casting. A lower end portion of the side wall portion 33 and an edge portion of the lower plate portion 32 are screwed and fastened to each other. The upper plate portion 31 is fixed to an upper end portion of the side wall portion 33 by crimping. The upper plate portion 31 includes an air inlet 311. The air inlet 311 is arranged above the impeller 4.
The motor portion 2 is of an outer-rotor type. The motor portion 2 includes a stationary portion 21, which is a stationary assembly, a rotating portion 22, which is a rotating assembly, and a sleeve 23, which is a bearing. The sleeve 23 is substantially cylindrical and centered on the central axis J1. The rotating portion 22 is supported by the sleeve 23 such that the rotating portion 22 is rotatable about the central axis J1 with respect to the stationary portion 21.
The stationary portion 21 includes a stator 210 and a bearing support portion 24. The bearing support portion 24 is arranged to accommodate the sleeve 23. The bearing support portion 24 is substantially cylindrical and centered on the central axis J1, and is made of a resin. The bearing support portion 24 is arranged to project upward from a substantial center of the lower plate portion 32. The bearing support portion 24 is fixed in a hole portion 327 defined in the lower plate portion 32. A lower end portion of the bearing support portion 24 and a portion of the lower plate portion 32 around the hole portion 327 are joined to each other by an insert molding process.
The stator 210 is an annular member centered on the central axis J1. The stator 210 is attached to an outside surface of the bearing support portion 24. The stator 210 includes a stator core 211, an insulator 212, and coils 213. The stator core 211 is defined by laminated silicon steel sheets, each of which is in the shape of a thin plate. The insulator 212 is made of an insulating material, and is arranged to cover a surface of the stator core 211.
The rotating portion 22 includes a shaft 221, a yoke 222, a rotor magnet 223, and a cup 224. The cup 224 has a bottom and is substantially cylindrical, and is centered on the central axis J1. The cup 224 is arranged to be open downwardly. The shaft 221 is centered on the central axis J1, and an upper end portion of the shaft 221 is fixed to the cup 224. The yoke 222 is substantially cylindrical and centered on the central axis J1, and is fixed to an inside surface of the cup 224. The rotor magnet 223 is substantially cylindrical and centered on the central axis J1, and is fixed to an inside surface of the yoke 222.
The shaft 221 is inserted in the sleeve 23. The sleeve 23 is defined by an oil-bearing porous metal body, and is inserted and fixed in the bearing support portion 24. Note that a ball bearing, for example, may be used as a bearing mechanism.
The impeller 4 includes a plurality of blades 41. The blades 41 are arranged on an outside of the cup 224 in an annular shape centered on the central axis J1. A radially inner end portion of each blade 41 is fixed to an outside surface of the cup 224. A torque centered on the central axis J1 is produced between the rotor magnet 223 and the stator 210 as a result of supply of a current to the stationary portion 21. The impeller 4 is thereby caused to rotate about the central axis J1 together with the rotating portion 22. Rotation of the impeller 4 causes an air to be drawn into the housing 3 through the air inlet 311, and to be sent out through the air outlet 331.
The first side wall portion 341 is arranged to extend in a curve along an outer circumference of the impeller 4. The first side wall portion 341 is arranged to extend in a circumferential direction about an axis displaced from the central axis J1. An inside surface of the first side wall portion 341 is also arranged to extend in a curve along the outer circumference of the impeller 4. That is, an inside surface 333 of the side wall portion 33 includes a curved surface 345 arranged to extend in a curve along the outer circumference of the impeller 4 on the opposite side of the impeller 4 with respect to the air outlet 331.
The second side wall portion 342 is arranged to extend from the first side wall portion 341 in a rotation direction of the impeller 4. The third side wall portion 343 is arranged to extend from the first side wall portion 341 in a direction opposite to the rotation direction of the impeller 4. The first side wall portion 341 is arranged to have a radial thickness smaller than the thickness of each of the second and third side wall portions 342 and 343 measured in a lateral direction in
Referring to
In the present preferred embodiment, each projection 346 is arranged on a portion of the side wall portion 33 which is arranged to project outward in a horizontal direction. Note, however, that the position of each projection 346 may be modified appropriately. In the present preferred embodiment, two of the crimping portions 344 are arranged in the first side wall portion 341, one of the crimping portions 344 is arranged in the second side wall portion 342, and one of the crimping portions 344 is arranged in the third side wall portion 343.
Referring to
Referring to
Provision of the flow control member 35 prevents a corner portion between the lower surface 312 of the upper plate portion 31 and the inside surface 333 of the side wall portion 33 from forming a right angle, and causes the lower surface 312 and the inside surface 333 to be joined to each other smoothly. This contributes to reducing a disturbance in an air which has been sucked in through the air inlet 311 by the impeller 4 and is now traveling radially outward, and smoothening a circumferential flow of the air. This results in an improved air blowing efficiency of the centrifugal fan 1. Moreover, the flow control surface 351 is arranged to be concave, being recessed toward the boundary 350, and this leads to an additional improvement in the air blowing efficiency of the centrifugal fan 1.
The flow control member 35 is bonded to both the lower surface 312 of the upper plate portion 31 and the inside surface 333 of the side wall portion 33. Here, the flow control member 35 being “bonded” to both the lower surface 312 and the inside surface 333 means that the flow control member 35 is so firmly adhered to both the lower surface 312 and the inside surface 333 that the flow control member 35 is not easily detached from the lower surface 312 or the inside surface 333. This bonding contributes to reducing vibrations of the upper plate portion 31 and the side wall portion 33. In particular, vibrations tend to occur with a high probability at an area between the two crimping portions 344 that are most distant from the air outlet 331, and provision of the flow control member 35 in this area leads to an effective reduction in the vibrations of the upper plate portion 31 and the side wall portion 33. Moreover, since crimping is additionally used to unite the upper plate portion 31 and the side wall portion 33 with each other, the upper plate portion 31 and the side wall portion 33 are firmly united with each other.
Note that the two crimping portions 344 that are most distant from the air outlet 331 refer to the most distant crimping portion 344 and the second most distant crimping portion 344. In other words, the two crimping portions 344 that are most distant from the air outlet 331 refer to a pair of adjacent ones of the crimping portions 344 in the side wall portion 33 that is most distant from the air outlet 331. Also note that, in the case where the air outlet 331 is a straight line in a plan view, the distance between the air outlet 331 and each crimping portion 344 refers to the distance between the straight line and the crimping portion 344, whereas in the case where the air outlet 331 is a curve in the plan view, the distance between the air outlet 331 and each crimping portion 344 refers to the distance between a straight line which is an approximation obtained by a least squares method or the like and the crimping portion 344.
According to the present preferred embodiment, because the first side wall portion 341 is thinner than each of the second and third side wall portions 342 and 343, the first side wall portion 341 tends to easily become a cause for vibrations. Even with this structure, provision of the flow control member 35 at a boundary between the upper plate portion 31 and the first side wall portion 341 reduces the vibrations effectively.
An oil-repellent agent is applied along the boundary 350 to define an oil-repellent film 36. A portion of the oil-repellent agent enters into a gap between the upper plate portion 31 and the side wall portion 33. In
The width of the flow control member 35 is arranged to gradually decrease toward an end point 353 at each end portion 352. The width of the flow control member 35 refers to the width of the flow control surface 351 in a section taken along a plane perpendicular to the boundary 350. The flow control surface 351 is accordingly arranged to approach the boundary 350 with decreasing distance from the end point 353. The flow control member 35 having such a shape contributes to reducing a disturbance in an air current at the end portion 352, and thereby preventing a decrease in the air blowing efficiency.
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, and that a variety of modifications are possible.
Although the flow control member 35 is arranged between the two crimping portions 344 in the first side wall portion 341 according to the above-described preferred embodiment, the arrangement of the flow control member 35 may be modified appropriately. For example, the flow control member 35 may be arranged to extend over the entire first side wall portion 341, or may be arranged to extend from the first side wall portion 341 into the second side wall portion 342 or the third side wall portion 343. That is, at least a portion of the flow control member 35 is arranged to extend along a boundary between the lower surface 312 of the upper plate portion 31 and the curved surface 345 of the side wall portion 33 illustrated in
Note that the air inlet may be defined in the lower plate portion 32. That is, the air inlet is defined in the upper plate portion 31 or the lower plate portion 32. The wording “the upper plate portion 31 or the lower plate portion 32” here means “at least one of the upper plate portion 31 and the lower plate portion 32”. Since provision of the air inlet reduces rigidity of the plate portion in which the air inlet is defined, it is preferable that the flow control member 35 should be arranged at the boundary between the inside surface 333 of the side wall portion 33 and the lower surface 312 of the upper plate portion 31 in the case where the air inlet is defined in the upper plate portion 31, and at a boundary between the inside surface 333 of the side wall portion 33 and an upper surface of the lower plate portion 32 in the case where the air inlet is defined in the lower plate portion 32. This contributes to reducing the vibrations. Note that the flow control member 35 may be arranged at a boundary between the side wall portion 33 and the plate portion in which the air inlet is not defined.
A structure in which the flow control member 35, made of the adhesive, is arranged at the boundary between the upper surface of the lower plate portion 32 and the inside surface 333 of the side wall portion 33 is also suitable for a reduction in the vibrations in the case where the lower plate portion 32 and the side wall portion 33 are united with each other by crimping.
Note that the flow control member 35 may be arranged at each of the boundary between the lower surface 312 of the upper plate portion 31 and the inside surface 333 of the side wall portion 33 and the boundary between the upper surface of the lower plate portion 32 and the inside surface 333 of the side wall portion 33. Also note that the flow control member 35 may be a member separately molded of a material other than the adhesive, e.g., a resin. In this case, the flow control member 35 is arranged on the boundary 350 through an adhesive or the like.
Note that the flow control surface 351 may not necessarily assume a concave shape in a vertical section taken along a plane including the central axis J1. For example, the flow control surface 351 may assume a straight line in the vertical section.
Also note that the oil-repellent film 36 may be omitted if the oil-repellent film 36 is not necessary to prevent the adhesive from leaking out of the housing 3. Also note that the oil-repellent film 36 may be replaced with another material.
Centrifugal fans according to preferred embodiments of the present invention are usable to cool devices inside chassis, for example, of notebook PCs and desktop PCs, to cool other devices, to supply an air to a variety of objects, and so on. Moreover, centrifugal fans according to preferred embodiments of the present invention are also usable for other purposes.
Features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-199628 | Sep 2012 | JP | national |
