AXIAL FLOW FAN AND HOUSING FOR THE SAME
An axial flow fan includes a housing that is formed by a process including injection molding includes a tapered surface at a frame portion thereof. One end of at least one rib is connected to an attachment portion which is a part of a stator portion of a motor portion, and the other end the rib is connected to a base portion protruding from the tapered surface. Two inclined surfaces connected to the tapered surface at the base portion and arranged in a circumferential direction with respect to a central axis are inclined such that the further a portion of the inclined surface from the central axis is, the further the portion is from a center of the rib. As a result, an air flow disturbance generated by the base portion between the rib and the frame portion is minimized, thereby reducing a noise generated due to the air flow disturbance.
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1. Field of the Invention
The present invention relates to a housing for an axial flow fan formed by a process including injection molding, and more particularly, to an axial flow fan utilizing the housing.
2. Description of the Related Art
Conventionally, a cooling fan such as an axial flow fan is used for cooling an interior portion of, or a specific member, in an electric component. The axial flow fan includes a motor portion including therein an impeller which rotates about a predetermined central axis, and a housing in which the motor portion is arranged. The housing includes a frame portion which surrounds a circumference of the motor portion and is centered about the central axis. Inside the frame portion, a stator portion of the motor is attached to an attachment portion which is located near one of the axial ends of the frame portion. Note, that the attachment portion can be a portion of the stator portion. The attachment portion is secured to the frame portion via a plurality of ribs extending in a direction that is perpendicular to the central axis toward an inner surface of the frame portion. In general, in a fan such as the one described above, the frame portion, the attachment portion and the plurality of ribs are integrally formed by a process including injection molding so as to reduce a production cost thereof.
Also, in recent years, in order to increase the cooling efficiency of the axial flow fan, a tapered surface is formed at a portion on the inner circumferential surface in which the rib is connected to the frame portion, wherein a distance between the tapered surface and the central axis gradually and continuously decreases toward a central area in an axial direction of the inner circumferential surface. However, such a housing is, due to structural restrictions imposed on a die assembly that is used for forming the housing, formed with a base portion protruding from the tapered surface. Normally, such a housing has a base portion which is larger in width in a circumferential direction than a rib.
In recent years, the demand for quieter electronic devices is increasing. Due to such demand, a quiet cooling fan used in the electronic device is also in demand. However, in the axial flow fan having the tapered surface on the housing thereof, an air flow generated by rotation of the impeller may be disturbed by the base portion inside the frame portion. Further, due to the air flow disturbance, noise will be generated when the fan is motion.
SUMMARY OF THE INVENTIONIn order to overcome the problems described above, preferred embodiments of the present invention reduce the noise generated by the air flow disturbance in the axial flow fan having the housing in which the tapered surface is formed by the process including injection molding.
According to a preferred embodiment of the present invention, an axial flow fan includes a housing that is operable to suppress an air flow disturbance within the axial flow fan so as to reduce a noise generated by the air flow disturbance. The housing for the axial flow fan is preferably formed by a process including injection molding and preferably includes an attachment portion included in a stator portion of a motor having therein an impeller, a frame portion surrounding a space in which the motor is arranged coaxially with a central axis of the motor, and at least one rib connecting the attachment portion and the frame portion. An inner circumferential surface of the frame portion has at least one tapered surface wherein a distance between the central axis and the tapered surface gradually decreases from a portion of the tapered surface in contact with the at least one rib to a portion of the tapered surface toward a rotor portion of the motor. The frame portion includes at least one base portion to which the at least one rib is connected and which protrudes from the at least one tapered surface. The base portion has at a portion thereof that is in contact with the rib, a surface on either sides of the rib, and one of the surfaces is inclined such that the further a portion of the inclined surface from the central axis is, the further from a center line of the rib the portion of the inclined surface is.
Other features, elements, processes, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.
According to preferred embodiments of the present invention, disturbance of an air flow within an axial flow fan is suppressed so as to reduce a noise which is generated by the air flow disturbance. The air flow disturbance is caused by a base portion provided between a rib of a housing, which has a tapered surface and is formed by a process including an injection molding, and an outer frame of the housing. In the description of the preferred embodiments of the present invention herein, words such as upper, lower, left, right, upward, downward, top, and bottom for explaining positional relationships between respective members and directions merely indicate positional relationships and directions in the drawings. Such words do not indicate positional relationships and directions of the members mounted in an actual device.
The rotor portion 21 includes an operative rotor portion 211 having a substantially cylindrical shape with its opening facing the stator portion 22, a ring shaped magnetic field magnet 212 which is magnetized to a plurality of magnetic poles and is centered around the central axis J1, wherein the magnetic field magnet 212 is affixed on an inner circumferential surface of the operative rotor portion 211. At a center of the operative rotor portion 211, an annular protruding portion 213 is provided. The annular protruding portion 213 is centered around the central axis J1 and protrudes toward the stator portion 22. One end (fixed end) of a shaft 214 is inserted into the annular protruding portion 213.
Also, the rotor portion 21 includes an impeller 215 which has a substantially cylindrical shape that is concentric with the central axis J1, in which the operative rotor portion 211 is inserted. The impeller includes a plurality of blades 21 on an outer circumferential surface thereof, and an annular shaped flange portion 217.
The stator portion 22 includes a substantially cylindrically shaped sleeve 221 which is preferably made of a porous metal material impregnated with oil, and a sleeve retaining portion 222 which is preferably made of a resin material. The sleeve 221 is inserted into the sleeve retaining portion 222 having the substantially cylindrical shape and a bottom. A non-fixed end of the shaft 214 is inserted into the sleeve 221. By virtue of the configuration, the shaft 214 is rotatably supported by the non-fixed end thereof through the oil and the sleeve 221. A thrust plate 223 facing the non-fixed end of the shaft 214 is provided at a bottom surface of the sleeve retaining portion 222. The thrust plate 223 is preferably made of a synthetic resin material having a low friction property, and supports the shaft 214. An armature 224 is arranged surrounding the sleeve retaining portion 222. The armature 224 is connected to an electric current supplying circuit 225. When the electric current controlled by the electric current supplying circuit 225 is supplied to the armature 224, a torque (a rotary force) is generated by a drive mechanism which includes the magnetic field magnet 212 and the armature 224 of the rotor portion 21 so as to rotate the rotor portion 21 with respect to the stator portion 22.
The housing 3 preferably includes an attachment portion 31 having a discoid shape that is centered around the central axis J1, and that is unitary and integral with the sleeve retaining portion 222 of the stator portion 22; a frame portion 32 having a ring shape that is centered around the central axis J1 so as to surround a circumference of the motor portion 2; and a plurality of ribs 33 each extending in a vertical manner with respect to the central axis J1 from the attachment portion 31 toward an inner surface of the frame portion 32. The attachment portion 31 is securely affixed to the frame portion 32 via the plurality of ribs 33. The inner surface of the frame portion 32 preferably includes a central circumferential surface 322 having a uniform distance between a mid point of the axial point in the axial direction and any mid point in the axial direction of the central circumferential surface 322 (that is, the central circumferential surface 322 is parallel or substantially parallel to the central axis J1); a tapered circumferential surface 321 whose distance to the central axis J1 increases toward a position where the rib 33 is arranged; a tapered circumferential surface 323 which is arranged at a portion near the central circumferential surface 322 opposite from the portion where the tapered circumferential surface 321 is arranged, and whose distance to the central axis J1 increases toward a portion farther away from the central circumferential surface 322. Note that, although a line defining the tapered surface 321 according to
In the axial flow fan 1, in order to blow air, air will be taken into the housing 3, due to the rotation of the impeller 215, from one end in the axial direction of the housing 3 (e.g., an end of the circumferential surface 323), then the air will be moved in accordance with the direction of the rotation of the impeller 215, and then the air will be exhausted from the other end in the axial direction of the housing 3 (e.g., an end of the tapered surface 321). Due to the tapered surface 321 and the circumferential surface 323 formed inside the frame portion 32 of the axial flow fan 1, an efficiency of the air flow as described above will be improved.
According to
Also, as described above, the frame portion 32 as shown in
Hereinafter, a connection between each of the plurality of ribs 33 and the frame portion 32 will be described in detail. As shown in
As seen in
Next, hereinafter, forming of the base portion 34 during a manufacturing of the housing 3 will be described. Note that, in order to effectively show the forming of the base portion 34, a position of the base portion 34 in the housing 3 shown in
The housing 3 according to the present preferred embodiment is preferably made of a resin material and is manufactured by injection molding utilizing predetermined die assemblies.
In
According to the manufacturing method of the housing 3 as shown in
Hereinafter, how the base portion 34 in the housing 3 is formed will be described with reference to
On the other hand, it is a prerequisite that a surface of each of two die assemblies, in contact with another surface, has a predetermined size and dimension in order to maintain durability of the connection between the top and the bottom die assemblies. Therefore, as for the top die assembly 91 and the bottom die assembly 92, a portion 923 (hereinafter, referred to as a “rib forming portion 923”; there is only one indication of the rib forming portion 923 in
It is to be appreciated that the bottom die assembly 92 is, in actuality, structured such that a diameter of the central circumferential surface 322 decreases slightly and continuously toward the tapered surface 321. By virtue of such a configuration, the bottom die assembly 92 can be separated effectively from the top die assembly 91 after the injection molding is completed.
Next, a conventional housing which is formed by an injection molding and which may be comparable to the housing 3 of the present preferred embodiment will be described.
Hereinafter, a result of a measurement of a noise generated by the axial flow fan 1 having therein the housing 3 will be compared to that generated by an axial flow fan having therein the housing 8. Preferably, a motor portion of each axial flow fan rotates at 3,200 rpm and has an impeller having 7 blades, and therefore, a first order component occurs at a frequency of 373 Hz ((3200/60)×7), for example.
According to
As described above, the housing 3 of the axial flow fan is formed by a process including injection molding and by the die assemblies. The housing 3 has the frame portion 32 at which the base portion 34 is provided for each rib 33 which is used for securing, via the base portion 34, the attachment portion 31. Also, each rib 33 has a pair of inclined surfaces 342 whose distance to the central axis J1 increases as the distance between the portion of the inclined surface 342 and the center line 331 increases. As a result of such a configuration, the axial flow fan 1 of the present preferred embodiment having therein the housing 3 which is formed by the process including injection molding and which includes therein at least one tapered surface increases the cooling efficiency. Also, the axial flow fan 1 of various preferred embodiments of the present invention having therein the housing 3 is operable to suppress the air flow disturbance caused by the base portion 34 which is disposed between the rib 33 and the frame portion 32, thereby reducing the noise generated due to the air flow disturbance.
According to the housing 3 as shown in
According to
While the preferred embodiments of the present invention have been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the present invention.
For example, although according to the housing 3 having the inclined surface 342 formed therein, the noise generated by the air flow disturbance will be minimized, the comparative exemplary housing 8 shown in
Further, when the inclined surface 342 is formed on one of the specific aspects of the base portion 34, the air flow disturbance will be suppressed to a certain extent. That is, it is important that at least one of the two specific aspects includes the inclined surface 342. Note that when only one of the specific aspects of each rib 33 includes the inclined surface 342, it is important that one specific aspect arranged on a same side with respect to each rib 33 is to include the inclined surface 342 so as to reduce the air flow disturbance.
Further, it is to be noted that only a certain portion of the specific aspect can be the inclined surface 342 in order to achieve the advantages described above. More particularly, it is preferable that the inclined surface be disposed at a portion of the specific aspect connected to the rib 33. Also, in order to effectively suppress the air flow disturbance when the inclined surface is to be disposed as mentioned above, it is preferable that, if the specific aspect extends in the same direction as that the rib 33 extends (as shown in
It is to be noted that in the housing 3, the inclined surface may have any shape as long as the inclined surface is shaped such that the further a portion of the inclined surface from the central axis J1 is, the further from the center line of the rib 33 it will be. For example, as shown in
Further, although the axial flow fan 1 according to
Further, although the housing 3 according to
Furthermore, note that in housing 3, the ribs 33 which connect the frame portion 32 to the attachment portion 31 need not extend perpendicularly to the central axis J1. The rib 33 may be tilted with respect to the perpendicular line to the axial direction.
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 the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
Claims
1. An axial flow fan having an injection molded housing, comprising:
- an attachment portion arranged to be provided in a stator portion of a motor having therein an impeller;
- a frame portion surrounding a space in which the motor is arranged and coaxial with a central axis of the motor; and
- at least one rib connecting the attachment portion and the frame portion; wherein
- an inner circumferential surface of the frame portion has at least one tapered surface wherein a distance between the central axis and the tapered surface gradually decreases from a portion of the tapered surface in contact with the at least one rib to a portion of the tapered surface extending toward a rotor portion of the motor;
- the frame portion includes at least one base portion to which the at least one rib is connected and which protrudes from the at least one tapered surface;
- the base portion has at the portion thereof in contact with the rib a surface on either side of the at least one rib, and one of the surfaces is inclined such that the further a portion of the inclined surface from the central axis is, the further from a center line of the rib the portion of the inclined surface is.
2. The axial flow fan having the housing according to claim 1, wherein the surfaces on either side of the at least one rib are inclined such that the further a portion of each of the inclined surface from the central axis is, the further from the center line of the rib the portion of the inclined surface is.
3. The axial flow fan having the housing according to claim 1, wherein the further the distance between a portion of the inclined surface and the central axis is, the greater an angle generated between the portion of the inclined surface and a center line of the rib becomes.
4. The axial flow fan having the housing according to claim 1, wherein the attachment portion is secured to the frame portion by a plurality of the ribs, and one of each pair of the surfaces disposed on a same side of each base portion of each rib includes the inclined surface.
5. The axial flow fan having the housing according to claim 1, wherein the inclined surface is injection molded.
6. The axial flow fan having the housing according to claim 5, wherein an outline of the frame has a shape including a straight line when viewed from an angle parallel to the central axis, a portion of the inner surface of the frame portion nearest to the straight line is a specific tapered surface at which an angle generated between the central axis and the specific tapered surface is smallest among any other portion of the inner surface of the frame portion, and the base portion is disposed on the specific tapered surface.
7. The axial flow fan having the housing according to claim 1, wherein, a portion of the rib and a portion of the base portion are connected to one another, and the further a portion of the rib from the central axis is, the wider the rib is.
8. An axial flow fan comprising:
- a motor, including: a rotor portion including an impeller; a stator portion; and
- an injection molded housing, including: an attachment portion provided in the stator portion; a frame portion surrounding a space in which the motor is arranged and coaxial with a central axis of the motor; and at least one rib connecting the attachment portion and the frame portion; wherein
- an inner circumferential surface of the frame portion has at least one tapered surface wherein a distance between the central axis and the tapered surface gradually decreases from a portion of the tapered surface in contact with the at least one rib to a portion of the tapered surface extending toward a rotor portion of the motor;
- the frame portion includes at least one base portion to which the at least one rib is connected and which protrudes from the at least one tapered surface;
- the base portion has at the portion thereof in contact with the rib a surface on either side of the at least one rib, and one of the surfaces is inclined such that the further a portion of the inclined surface from the central axis is, the further from a center line of the rib the portion of the inclined surface is.
Type: Application
Filed: Feb 13, 2007
Publication Date: Aug 16, 2007
Applicant: NIDEC CORPORATION (Kyoto)
Inventor: Yoshiaki OGUMA (Kyoto)
Application Number: 11/674,396
International Classification: F04D 29/44 (20060101);