1. Field of the Invention
The present invention relates to a fan unit, and more specifically to a fan unit including a plurality of axial fans connected in series.
2. Description of the Related Art
Cooling fans are used for cooling electronic parts inside a casing of various electronic devices. The cooling fans are required to have improved air flow characteristics, i.e., an improved static pressure vs. flow rate curve with an increase in the amount of heat generation associated with a performance improvement of the electronic parts and the increase in the density of the electronic parts associated with a size reduction of the casing. As an exemplary cooling fan which can provide a sufficient static pressure and a sufficient flow rate, a serial axial fan unit is currently used which includes a plurality of axial fans connected in series.
An advantage of preferred embodiments of the present invention is a reduction in the turbulence in air flow caused by support ribs in a serial axial fan while still ensuring rigidity of the support ribs.
According to a preferred embodiment of the present invention, there is provided a serial axial fan including first and second axial fans. The first axial fan preferably includes a first base portion, a first motor portion supported by the first base portion, a first impeller including a plurality of first blades, a first housing arranged to enclose an outer circumference of the first impeller, and a plurality of first support ribs arranged to connect the first base portion to the first housing. The second axial fan preferably includes a second base portion, a second motor portion supported by the second base portion, a second impeller including a plurality of second blades, a second housing arranged to enclose an outer circumference of the second impeller, and a plurality of second support ribs arranged to connect the second base portion to the second housing. The first and second axial fans are coupled to each other with the first and second base portions either in contact with or in close proximity to each other (i.e., are adjacent to each other but not in contact with one another). A portion of each of the first support ribs on the first impeller side is positioned within the first housing, while a portion on the second impeller side of each of the first support ribs is positioned within the second housing. A portion of each of the second support ribs on the second impeller side is positioned within the second housing, while a portion on the first impeller side of each of the second support ribs is positioned within the first housing.
The serial axial fan according to the various preferred embodiments of the present invention achieves a reduction in the turbulence in air flow caused by the support ribs while ensuring the rigidity of the support ribs.
Other features, elements, 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.
Serial axial fans according to preferred embodiments of the present invention include first and second axial fans. Each of the first and second axial fans preferably includes a plurality of support ribs arranged to connect a base portion and a housing to one another. The first and second axial fans are coupled to each other with their respective base portions either in contact with or in close proximity to each other. Each of the support ribs in each of the first and second axial fans extends over the housings of both the first and second axial fans.
Hereinafter, the present invention will be described with reference to the preferred embodiments.
First Preferred Embodiment
The serial axial fan 1 is a so-called counter-rotating axial fan. In the serial axial fan 1, air is drawn in from above the first axial fan 2 as in
In the following description, as regards directions parallel or substantially parallel to the central axis J1, the upper side in
The first impeller 21 preferably includes a plurality of first blades 211 and a cup 212, which substantially has the shape of a covered cylinder and is arranged to cover the exterior of the first motor portion 22. The first blades 211 extend radially outward from an outer side surface of the cup 212, and are arranged at regular intervals in a circumferential direction. The first motor portion 22 includes a first rotor portion 221, i.e., a rotor, and a first stator portion 222, i.e., a stator. The first rotor portion 221 is arranged on the upper side of the first stator portion 222 along the central axis J1.
The first rotor portion 221 preferably includes a metallic yoke 2211, a substantially cylindrical field magnet 2212, and a shaft 2213. The metallic yoke 2211 substantially has the shape of a covered cylinder, and is centered about the central axis J1. The field magnet 2212 is substantially cylindrical and fixed to an inside of the yoke 2211. The shaft 2213 extends downward from a center of an upper portion of the yoke 2211. The yoke 2211 in the first rotor portion 221 is preferably covered by the cup 212, so that the first rotor portion 221 is combined with the first impeller 21.
The first stator portion 222 includes a bearing support portion 2221, an armature 2222, and a circuit board 2223. The bearing support portion 2221 is substantially cylindrical, and extends upward from a center of the first base portion 24. The armature 2222 is attached to an outer circumference of the bearing support portion 2221. The circuit board 2223 is preferably arranged below the armature 2222, and electrically connected to the armature 2222. The armature 2222 is arranged radially opposite the field magnet 2212. Ball bearings 2224 and 2225 are spaced apart from each other at upper and lower positions inside the bearing support portion 2221 along the central axis J1 to define a bearing mechanism. The shaft 2213 inserted in the bearing support portion 2221 is rotatably supported by the ball bearings 2224 and 2225.
The second axial fan 3 preferably has substantially the same shape and structure as those of the first axial fan 2 turned upside down. Therefore, the above description of the first axial fan 2 can be applied as a description of the second axial fan 3 by replacing the term “first axial fan 2” with the term “second axial fan 3”, and “first” with “second” in the terms of the components, and changing a starting numeral of each reference numeral from “2” to “3”. For example, the term “first impeller 21” in the description of the first axial fan 2 is replaced with the term “second impeller 31” in the description of the second axial fan 3.
Similarly, a second motor portion 32 has the substantially same structure as the first motor portion 22. Therefore, the above description of the first motor portion 22 can be applied as a description of the second motor portion 32 in a similar manner.
In the first axial fan 2 of the serial axial fan 1, the first motor portion 22 causes the first impeller 21 to rotate to produce air flow along the central axis J1. In the second axial fan 3, the second motor portion 32 causes the second impeller 31 to rotate in a direction opposite to a rotation direction of the first impeller 21, to produce air flow in the same direction as that of the air flow produced by the first impeller 21. Thus, the direction of the whirling components of the air flow produced by the first impeller is changed efficiently by the second impeller rotating in the opposite direction to the rotation direction of the first impeller. This arrangement contributes to an improvement in static pressure while securing sufficient air flow volume.
In this manner, the first support rib 25 extends across a boundary between the first and second base portions 24 and 34.
In this exemplary serial axial fan, the first and second housings 23 and 33 are placed one upon the other. In this situation, the two first support ribs 25 and the two second support ribs 35 combine to define a support rib set. In the support rib set, the first and second support ribs 25 and 35 are alternately arranged at regular intervals in the circumferential direction.
The second support ribs 35 have substantially the same shape as that of the first support ribs 25 as illustrated in
The slant of each of the first and second support ribs may also be understood as follows. That is, it is preferable that each of the first and second support ribs project in such an orientation as to substantially follow the direction of the air flow produced by the first impeller, and be slanted with respect to the direction parallel to the central axis J1.
In this manner, the second support rib 35 extends across the boundary between the first and second base portions and 34.
The first and second support ribs 25 and 35 in the exemplary serial axial fan 1 described above may also be understood as follows. That is, each of the first support ribs has a portion that protrudes toward the second housing 33 to be inserted into the second housing 33, whereas each of the second support ribs 35 has a portion that protrudes toward the first housing 23 to be inserted into the first housing 23.
Referring to
When the first and second axial fans 2 and 3 are coupled together, the first and second housings 23 and 33 are first arranged to be substantially coaxial with and opposite to each other. At this time, referring to
Next, the first and second housings 23 and 33 are brought closer to each other so that the lower end portion of the first housing 23 and the upper end portion of the second housing 33 are brought into contact with each other, and the first and second base portions 24 and 34 are brought into contact with each other. In this manner, the first and second axial fans 2 and 3 are coupled together.
At this time, as illustrated in
Thereafter, the through holes 2311 (see
In the serial axial fan 1 as described above, as illustrated in
The structure of the serial axial fan 1 according to the first preferred embodiment and an operation of fixing the first and second axial fans 2 and 3 together have been described above.
Notice here that in related-art serial axial fans, support ribs in two fans are placed one upon the other in the direction parallel to the central axis J1. As such, a slight gap or displacement between the associated support ribs causes turbulence in the air flow.
In contrast, in the serial axial fan 1 according to the first preferred embodiment, the first and second support ribs 25 and 35, which combine to define the support rib set, are alternately arranged at regular intervals in the circumferential direction, as described above. Since no two support ribs are placed one upon the other, a reduction in the turbulence in the air flow caused by the support ribs is achieved. This contributes to reducing noise and a decrease in the volume of air exiting the fan.
In addition, arranging the first and second support ribs 25 and 35 at regular intervals in the circumferential direction contributes to a further reduction in the turbulence in the air flow. Moreover, the substantially same shape of the first and second support ribs 25 and 35 also contributes to a further reduction in the turbulence in the air flow.
As described above, both the first and second support ribs 25 and 35 extend across the boundary between the first and second base portions 24 and 34. In other words, regarding each of the first and second support ribs 25 and 35, upper and lower edges of the support rib, extending along a direction in which the support rib extends (a substantially radial direction), are positioned within the first and second housings 23 and 33, respectively. This enables the support ribs to have a sufficiently large dimension in a direction substantially parallel to the central axis J1, to ensure rigidity of the support ribs.
Moreover, the first and second support ribs 25 and 35 are arranged alternately in the circumferential direction. This enables the first base portion 24 of the first axial fan 2 and the second base portion 34 of the second axial fan 3 to be securely supported.
As described above, in the serial axial fan 1, the first and second base portions 24 and 34, which are individual integral portions, are fixed together via the two pairs of engagement portions. This allows vibration components in the first and second base portions 24 and 34 to cancel each other out. This contributes to reducing the vibration in the first and second base portions 24 and 34.
Still further, since the first and second base portions 24 and 34 are fixed together, the distribution of natural frequencies of the serial axial fan 1 is such that unfavorable vibration components are reduced, as compared with that of a serial axial fan in which base portions are not fixed together.
Second Preferred Embodiment
According to the second preferred embodiment, in the first axial fan 2, four first support ribs 25a are arranged at regular intervals in the circumferential direction. The first support ribs 25a are different in shape from the first support ribs 25 in the first axial fan 2 as illustrated in
In the serial axial fan according to the second preferred embodiment, the four first support ribs 25a as illustrated in
Although not shown in
In the second preferred embodiment, as well as in the first preferred embodiment, the first and second base portions 24 and 34 are fixed together via the pairs of first and second engagement portions 41 and 42. In the following description, members or portions that have equivalents in the serial axial fan 1 are assigned the same reference numerals as their equivalents.
As illustrated in
In each of the first support ribs 25a, the lower portion 251, which protrudes downward relative to the first base portion 24, and the remaining portion, excluding the lower portion 251, are positioned within the second housing 33 and the first housing 23, respectively. Thus, the lower portion 251 and the remaining portion, excluding the lower portion 251, can be considered as a portion for the second impeller 31 (see
As illustrated in
In each of the second support ribs 35a, the upper portion 351, which protrudes upward relative to the second base portion 34, and the remaining portion, excluding the upper portion 351, are positioned within the first housing 23 and the second housing 33, respectively. Thus, the upper portion 351 and the remaining portion, excluding the upper portion 351, can be considered as a portion of the first impeller 21 and a portion of the second impeller 31, respectively.
In the serial axial fan according to the second preferred embodiment, the first and second support ribs 25a and 35a, which combine to define the support rib set, are alternately arranged at regular intervals in the circumferential direction. That is, no two support ribs are placed one upon the other. Therefore, as in the first preferred embodiment, a reduction in the turbulence in the air flow is achieved.
Both the first and second support ribs 25a and 35a extend across the boundary between the first and second base portions 24 and 34. Therefore, as in the first preferred embodiment, the rigidity of the support ribs is ensured.
Third Preferred Embodiment
The third preferred embodiment adopts a different engagement mechanism from the first and second engagement portions used in the first and second preferred embodiments described above.
The first axial fan according to the third preferred embodiment is preferably identical in structure to the first axial fan 2 as illustrated in
When the first and second axial fans are coupled together, the first and second housings 23 and 33 are first arranged to be coaxial or substantially coaxial with and opposite to each other, while the associated corner portions thereof are displaced one from the other in the circumferential direction. In this situation, where the associated corner portions are displaced one from the other in the circumferential direction, the first engagement portion 41a is positioned opposite to the first groove portion 431 of the second engagement portion 43.
Next, the first and second housings 23 and 33 are brought closer to each other so that the lower end portion of the first housing 23 and the upper end portion of the second housing 33 are brought into contact with each other, and the first and second base portions 24 and 34 are brought into contact with each other. At this time, the first engagement portion 41a is inserted into the first groove portion 431 of the second engagement portion 43.
Then, the first housing 23, which is in contact with the second housing 33, is turned in the circumferential direction relative to the second housing 33, so that the lower end portion 413 of the first engagement portion 41a is moved into the second groove portion 432 of the second engagement portion 43. As a result, the lower end portion 413 of the first engagement portion 41a and the second groove portion 432 of the second engagement portion 43 are engaged with each other, as illustrated in
In the third preferred embodiment, the first and second base portions 24 and 34 are fixed together via the first and second engagement portions 41a and 43. Therefore, a reduction in vibration is achieved as in the first preferred embodiment.
Other Preferred Embodiments
Some exemplary preferred embodiments of the present invention have been described above. Note, however, that the present invention is not limited to the preferred embodiments described above, and that various other modifications are possible.
For example, the number of first support ribs 25, 25a and the number of second support ribs 35, 35a may be increased or decreased to any desirable number.
Specifically, both the number of first support ribs 25a and the number of second support ribs 35a in the second preferred embodiment may be changed to two. The first and second support ribs 25a and 35a are also alternately arranged at regular intervals in the circumferential direction in a support rib set composed of the two first support ribs 25a and the two second support ribs 35a.
Further, the number of first support ribs 25, 25a and the number of second support ribs 35, 35a may be different from each other. Even in this case, a reduction in the turbulence in the air flow in the serial axial fan can be achieved by arranging a plurality of first support ribs and a plurality of second support ribs, which combine to define a support rib set, at regular intervals in the circumferential direction.
In the above-described preferred embodiments, the lower portion 251 of each of the first support ribs 25, 25a may not necessarily be in contact with the second base portion 34 and the second housing 33 but may only be in close proximity to the second base portion 34 and the second housing 33. The same is true for the upper portion 351 of each of the second support ribs 35, 35a.
In the above-described preferred embodiments, a reduction in the turbulence in the air flow is achieved due to the slant of the first support ribs 25, 25a and the second support ribs 35, 35a being substantially parallel to the direction of the air flow.
In the case where the influence of the support ribs on the air flow is slight, the support ribs may be substantially flat, with cross-sections perpendicular to the central axis J1 defining the shape of a long and narrow rectangle.
It is preferable that the support ribs be substantially flat, but the support ribs may have any desirable shape. For example, each of the support ribs may be bar-shaped, with cross-sections perpendicular to a direction in which the support rib extends defining the shape of a triangle. In this case, it is preferable that each of the support ribs have a surface slanted so as to follow the direction of the air flow, in order to achieve a reduction in the turbulence in the air flow. Even such support ribs can have a sufficiently large dimension in the direction parallel to the central axis J1 when a portion thereof on the first impeller 21 side is positioned within the first housing 23 and a portion thereof on the second impeller 31 side is positioned within the second housing 33, to ensure the rigidity of the support ribs.
In the above-described preferred embodiments, the first and second base portions 24 and 34 may not necessarily be in contact with each other, but may only be in close proximity to each other. Even in this case, relative positions of the first and second base portions 24 and 34 can be fixed by use of the two first engagement portions 41 and the two second engagement portions 42.
Also, the first and second axial fans 2 and 3 according to a preferred embodiment of the present invention may be used as two axial fans connected in series within a serial axial fan including three or more axial fans. In other words, the shapes of the support ribs and the methods of fixing the first and second base portions 24 and 34 together as described above with reference to the preferred embodiments may be used in two axial fans within a serial axial fan including three or more axial fans connected in series.
Further, in general, the rotation direction of the second axial fan arranged downstream may be either a clockwise or counterclockwise direction. For example, in the preferred embodiments described above, the first and second impellers 21 and 31 in the serial axial fan may be arranged to rotate in the same direction. In this case, it is preferable that the support ribs be shaped as stationary vanes, as the first and second support ribs 25a and 35a.
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.
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