The present invention relates to an axial flow fan used for cooling an inside of electrical equipment or the like.
When the size of electrical equipment is reduced, a space in which air flows inside a casing of the electrical equipment is also reduced. For this reason, as a fan used for cooling an inside of the casing, the fan characterized by an increased air volume and a higher static pressure is demanded. In the fan having such characteristics, it is also demanded to reduce noise as much as possible.
U.S. Pat. No. 6,244,818 or Japanese Patent Publication No. 2000-257597 (Patent Document 1), for example, discloses an axial flow fan including an impeller having nine rotary blades and 13 stationary blades disposed on the side of a discharge opening to fulfill this demand, as shown in FIGS. 1 and 4 of Patent Document 1.
It has been confirmed when a plurality of stationary blades are provided, the demand described above may be fulfilled. Recently, however, depending on an application, a higher performance fan is sometimes demanded, compared with existing axial flow fans including the stationary blades.
An object of the present invention is to provide an axial flow fan which attains more air volume and higher static pressure than ever.
Another object of the present invention is to provide an axial flow fan in which noise may be reduced more than ever.
An axial flow fan of the present invention includes a housing, an impeller, a motor that rotates the impeller, and a plurality of stationary blades. The housing includes an air channel portion having a suction opening on one side of an axial direction of a rotary shaft and a discharge opening on the other side of the axial direction. The impeller includes a plurality of rotary blades that rotate within the air channel portion. The rotary blades are disposed in a circumferential direction of the rotary shaft at equidistant intervals. The motor causes the impeller to rotate about the rotary shaft in one rotating direction. The stationary blades are disposed in the vicinity of the discharge opening of the air channel portion. The stationary blades are disposed in the circumferential direction of the rotary shaft at equidistant intervals. In the present invention, the number of the rotary blades is seven (7), and the number of stationary blades is eight (8).
The inventors of the present invention studied a relationship of the number of rotary blades and the number of stationary blades with characteristics of the fan. The study has confirmed that the combination of seven rotary blades and eight stationary blades may increase the air volume and static pressure of the fan, compared with other combination in numbers of rotary and stationary blades. The study has also confirmed that, with this combination of rotary and stationary blades in number, noise generation may also be reduced more than other combinations. Therefore, the fan of the present invention may increase the air volume and static pressure more than ever, and may also reduce noise generation.
Preferably, the rotary blade may have a cross-sectional shape which is curved to form a concave portion opened toward one rotating direction of the impeller as the rotary blade is cross-sectioned in an orthogonal direction to the axial direction. In this case, the cross-sectional shape of the rotary blade is curved to form a convex portion raised toward an opposite direction to the one rotating direction as the rotary blade is cross-sectioned in the axial direction. Preferably, the stationary blade has a cross-sectional shape which is curved to form a concave portion opened toward an opposite direction to the one rotating direction as the stationary blade is cross-sectioned in an orthogonal direction to the axial direction. In this case, the cross-sectional shape of the stationary blade is curved to form a convex portion raised toward the one rotating direction as the stationary blade is cross-sectioned in the axial direction. Specifically, when the rotary and stationary blades are respectively shaped as described above, both of the maximum air volume and the maximum static pressure may be increased while suction noise may be reduced.
The impeller includes a rotary blade fixing member having a peripheral wall portion onto which the rotary blades are fixed. The stationary blades respectively have an outside end portion fixed to the inner wall portion of the air channel portion, and an inside end portion located opposite to the outside end portion in a radial direction of the rotary shaft. A stationary blade fixing member is disposed in a central portion of the air channel portion in the vicinity of the discharge opening of the air channel portion. The stationary blade fixing member includes a peripheral wall portion having an outer diameter which is equal to or smaller than an outer diameter of the peripheral wall portion of the rotary blade fixing member. With this arrangement, the stationary blade fixing member will not become a great resistance against an air flow generated by means of ration of the impeller. The inside end portion of each of the stationary blades is fixed onto the peripheral wall portion of the stationary blade fixing member. Accordingly, the stationary blade fixing member is fixed onto the housing by the stationary blades. The stationary blade fixing member may support a stator of the motor and a bearing that rotatably supports the rotary shaft.
Preferably, the stationary blades may respectively be shaped so that a side of the outside end portion that extends along the inner wall portion may be longer than a side of the inside end portion that extends along the peripheral wall portion of the stationary blade fixing member. More preferably, the stationary blades are respectively shaped as follows. First, it is assumed that a first hypothetical plane extends in a radial direction of the rotary shaft, passing through an end, located closest to the discharge opening, of the side of the inside end portion of the stationary blade and containing a centerline passing through the center of the rotary shaft. Next, it is assumed that a second hypothetical plane extends in the radial direction, passing through an end, located closest to the discharge opening, of the side of the outside end portion of the stationary blade and containing the centerline. Further, it is assumed that a third hypothetical plane extends in the radial direction, passing through an end, located closest to the suction opening, of the side of the outside end portion of the stationary blade and containing the centerline. Then, the stationary blades are respectively shaped so that a direction from the first hypothetical plane to the second hypothetical plane and a direction from the second hypothetical direction to the third hypothetical direction are respectively opposite to the one rotating direction of the impeller. When the shape of each of the stationary blades is determined as described above, the stationary blades may readily be shaped according to a desired characteristic. In this case, if an angle θ1 formed between the first hypothetical plane and the second hypothetical plane is larger than an angle θ2 formed between the second hypothetical plane and the third hypothetical plane, an air volume may be increased. Preferably, the angle θ1 is within the range of 25 to 30 degrees, and the angle θ2 is within the range of 15 to 20 degrees. With these angle settings, it may become easy to design an axial flow fan which attains more air volume and higher static pressure.
Preferably, the length of the side of the outside end portion of the stationary blade corresponds to 40 to 50% of the length of the rotary blade extending in the axial direction. With this length setting, it may become easy to design an axial flow fan which attains more air volume and higher static pressure.
A plurality of lead wires are sometimes used to supply electric power to the motor without using electrical connectors. In this case, the lead wires inevitably pass through an air channel in order that the lead wires may be pulled out from the housing. For this purpose, a lead wire engaging portion is provided to engage with the lead wires. The lead wire engaging portion is disposed at a wall portion surrounding the discharge opening of the air channel portion of the housing, and is configured to engage with the lead wires connected to the motor. Presence of the lead wires may not only affect the air volume and static pressure, but also may cause noise generation. Then, preferably, a guide wall portion may be provided to form a guide groove between the guide wall portion and one of the stationary blades, disposed in the vicinity of the lead wire engaging portion. The guide groove receives the lead wires therein and guides the lead wires to the lead wire engaging portion. When the guide wall portion as described above is provided and a plurality of lead wires are received in the guide groove, presence of the lead wires may have less adverse effect on the air volume and static pressure and may generate less noise.
As described above, each of the stationary blades includes an outside end portion fixed to an inner wall portion of the air channel portion and an inside end portion located opposite to the outside end portion in a radial direction of the rotary shaft. A stationary blade fixing member is disposed in a central portion of the air channel portion in the vicinity of the discharge opening. The stationary blade fixing member includes a peripheral wall portion onto which the inside end portion of each of the stationary blades is fixed. The guide wall portion includes a first end portion located on a side of the suction opening, a second end portion located on a side of the discharge opening, a third end portion located on a side of the inner wall portion of the air channel portion, and a fourth end portion located on a side of the stationary blade fixing member. Then, the first end portion of the guide wall portion extends from the inner wall portion of the air channel portion toward the stationary blade fixing member and is coupled to a suction-side end portion of the one stationary blade, located on the side of the suction opening, thereby forming the guide groove between the guide wall portion and the one stationary blade. With this arrangement, presence of the guide wall portion may suppress adverse effect on the relationship of the static pressure to the air volume and may also reduce noise generation.
Preferably, the third end portion of the guide wall portion is fixed to the inner wall portion of the air channel portion. When the guide wall portion is structured as described above, mechanical strength of the guide wall portion may be increased.
Preferably, the coupling portion between the first end portion and the suction-side end portion of the one stationary blade is shaped so as to become thinner toward the suction opening. With this arrangement, the coupling portion may be prevented from becoming a great resistance against an air flow generated by means of rotation of the impeller.
Further, it is preferable that the second end portion of the guide wall portion may be flush with a hypothetical opening surface of the discharge opening. In this case, it is preferable that the guide wall portion may extend from the first end portion to the second end portion so that the guide wall portion may substantially become orthogonal to the hypothetical opening surface of the discharge opening. When the guide wall portion is provided as described above, a resistance against an air flow, generated due to the presence of the guide wall portion, may be further reduced.
The lead wire engaging portion may include a through hole formed in the housing and disposed adjacent to the outside end portion of the one stationary blade, and a slit formed in the housing. The through hole communicates an inside of the air channel portion with an outside of the housing. The slit communicates with the through hole and is opened to the other side of the axial direction. In this case, a size of the slit is determined so that the lead wires, which are received in the guide groove and go out via the through hole, do not readily get out of the slit. When the lead wire engaging portion is configured as described above, the lead wires may readily be inserted into the guide groove and pulled out to the outside of the housing. When the lead wire engaging portion is configured as described above, it is preferable that the third end portion of the guide wall portion may be fixed to the inner wall portion of the air channel portion. Then, it is preferable that a length of the guide wall portion extending along the one stationary blade may be determined so as to prevent a part of an air flow generated by means of rotation of the impeller from actively flowing out to the outside of the housing via the through hole. With this arrangement, the air flow substantially does not go out via the through hole, thereby generating less noise.
An axial flow fan according to an embodiment of the present invention will be described below in detail with reference to drawings.
Referring to these drawings, the axial flow fan 1 includes a housing 3, an impeller 7 including seven rotary blades 5 that are disposed inside the housing 3 and rotate, a motor 9 including a rotary shaft 8 to which the impeller 7 is attached, and eight stationary blades 11. As shown in
The suction-side flange 13 has substantially a square contour shape, and has a suction opening 14 of substantially a circular shape. The suction-side flange 13 has a flat surface 13a at each of four corner portions thereof. In each of the four corner portions, a through hole 13b, through which a mounting screw passes, is formed.
The discharge-side flange 15 also has substantially a square contour shape, and has a discharge opening 16 of substantially a circular shape. The discharge-side flange 15 has a flat surface 15a at each of four corner portions thereof. In each of the four corner portions, a through hole 15b, through which a mounting screw passes, is formed.
The impeller 7 includes a rotary blade fixing member 6 of a cup shape. Seven rotary blades 5 are fixed to a peripheral wall portion of the rotary blade fixing member 6. A plurality of permanent magnets that constitute a part of a rotor of the motor 9 are fixed onto the inside of the peripheral wall portion of the rotary blade fixing member 6.
As shown in
As shown in
As shown in
Referring to
As shown in
The lead wire engaging portion 25 to engage with the three lead wires 10 is provided at the housing 3. The lead wire engaging portion 25 includes a through hole 27 that is formed in the cylindrical portion 17 of the housing 3, being disposed adjacent to the outside end portion 11A of an adjacent stationary blade 11, and a slit 29 formed in the flange 15 of the housing 3. The through hole 27 communicates an inside of the air channel portion 19 with an outside of the housing 3. The slit 29 communicates with the through hole 27 and is opened to the other side of the axial direction. In this case, a width of the slit 29 is determined so that the three lead wires 10 may not readily get out of the slit 29. The three lead wires 10 are received in a guide groove 31, which will be described later, and go out via the through hole 27. When the lead wire engaging portion 25 is configured as described above, the lead wires 10 may readily be inserted into the guide groove 31 and pulled out of the housing 3. In this embodiment, at the flange 13 of the housing 3 as well, a lead wire engaging portion 26 is formed to engage with the lead wires 10 bent along the cylindrical portion 17.
In this embodiment, as shown in
The third end portion 39 of the guide wall portion is fixed to the inner wall portion of the air channel portion 19. As shown in
Further, in this embodiment, the second end portion 37 of the guide wall portion 33 is flush with a hypothetical opening surface of the suction opening 16. In this case, the guide wall portion 33 extends from the first end portion 35 to the second end portion 37 so that the guide wall portion 33 may substantially become orthogonal to the hypothetical opening surface of the opening portion 16 or may become parallel to the rotary shaft 8. When the guide wall portion 33 is provided as described above, a resistance against an air flow, generated due to presence of the guide wall portion 33, may be further reduced. As a result, when the guide wall portion 33 as described above is provided and a plurality of lead wires are received in the guide groove, presence of the lead wires may have less adverse effect on the air volume and static pressure, and may generate less noise.
In this embodiment, a length L4 (refer to
Further, air volume-static pressure characteristics were measured in both cases where the guide wall portion 33 was provided and where the guide wall portion 33 was not provided, in order to confirm effect brought about by providing the guide wall portion 33. Also, a sound pressure level was measured. Results of measurement of the air volume-static pressure characteristics are shown in
Next, a test was conducted where the number of the rotary blades 5 and the number of the stationary blades 11 were changed so as to confirm that characteristics of the axial flow fan in this embodiment are excellent.
Table 1 below shows results of measurement of the sound pressure level when the number of the rotary blades was fixed and the number of the stationary blades was changed, and when the number of the rotary blades was changed and the number of the stationary blades was fixed.
The sound pressure level is shown as a change in the sound pressure level when the guide wall portion 33 is removed, provided that the sound pressure level with the lead wires received in the guide groove 31 is defined as Lp[dB(A)]. More specifically Lp+5 [dB(A)] indicates that the sound pressure level increased by 5 [dB(A)] from the sound pressure level of Lp[dB(A)] when the lead wires were received in the guide groove 31. It can be seen from Table 1 that the sound pressure level increased except in cases where the numbers of the rotary blades and the stationary blades were seven and eight, respectively, and where the numbers of the rotary blades and the stationary blades were seven and six, respectively. In both cases, the sound pressure level remained unchanged.
It can be seen from the results of measurement described above that the maximum air volume may be increased, the maximum static pressure may be increased, and suction noise may also be reduced when the number of the rotary blades is seven and the number of the stationary blades is eight, as in the axial flow fan of this embodiment. A simulation confirmed that this tendency also appeared even when the shape of the rotary blades and the shape of the stationary blades were changed.
According to an axial flow fan of the present invention, both of the air volume and static pressure of the fan may be increased more than ever by defining a relationship in numbers of rotary and stationary blades. In addition, noise generation may also be reduced.
Number | Date | Country | Kind |
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2005-031097 | Feb 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2006/301737 | 2/2/2006 | WO | 00 | 8/6/2007 |
Publishing Document | Publishing Date | Country | Kind |
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WO2006/082876 | 8/10/2006 | WO | A |
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Number | Date | Country | |
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20090010759 A1 | Jan 2009 | US |