The present invention relates to a counter-rotating axial-flow fan used to cool an interior of an electric appliance.
As an electric appliance becomes smaller in size, so does a space inside a case of the electric appliance in which air flows. To cool an interior of the small case, a fan with features of a large amount of air and a high static pressure is called for. As a fan with such features, a counter-rotating axial-flow fan has come to be used in recent years.
For example, Japanese Patent Publication No. 2004-278370 (US2005/0106026) (FIG. 1) shows a conventional counter-rotating axial-flow fan of this kind.
In recent years some applications call for higher performance than that of the existing counter-rotating axial-flow fan.
An object of the present invention is to provide a counter-rotating axial-flow fan which is capable of producing a larger amount of air and a higher static pressure than conventional fans do.
The counter-rotating axial-flow fan or axial-flow fan with double impellers rotating in mutually opposite directions of this invention comprises a housing, a first impeller, a first motor, a second impeller, a second motor, and a plurality of stationary blades. The housing includes an air channel which has a suction opening portion at one side in an axial direction thereof and a discharge opening portion at the other side in the axial direction. The first impeller includes a plurality of front blades that rotate in the suction opening portion. The first motor rotates the first impeller about an axial line of the fan in one of two rotating directions. The second impeller has a plurality of rear blades that rotate in the discharge opening portion. The second motor rotates the second impeller about the axial line in the other rotating direction opposite to the one rotating direction. The stationary blades are arranged stationary in the housing between the first impeller and the second impeller and extend radially. Here, the word “radially” applies to not only a case where the blades extend radially in straight lines but also a case where they extend radially in curved lines. In the counter-rotating axial-flow fan of the present invention, the number of the plurality of front blades is defined to be N, the number of the plurality of stationary blades is defined to be M, and the number of the plurality of rear blades is defined to be P. Each of N, M and P is a positive integer, and their relationship is defined as N>P>M.
In the counter-rotating axial-flow fan of this invention, a length L1 of each of the N front blades, measured in the axial direction is defined to be longer than a length L2 of each of the P rear blades, measured in the axial direction. A relationship between the length L1 and the length L2 has been studied. The finding is that a larger amount of air and a higher static pressure can be generated when the length L1 is set longer than the length L2. In the counter-rotating axial-flow fan of this invention, the air amount and the static pressure can be increased, compared with conventional fans.
The first impeller includes an annular member having a peripheral wall on which N blades are mounted and disposed at a predetermined interval in a circumferential direction. End portions of the N blades, located at the other side in the axial direction, extend toward the other side beyond an end portion of the peripheral wall of the annular member, located at the other side in the axial direction. The second impeller includes an annular member having a peripheral wall on which the P blades are mounted and disposed at a predetermined interval in a circumferential direction. End portions of the P blades, located at the one side in the axial direction, do not substantially extend beyond an end portion of the peripheral wall of the annular member located at the one side in the axial direction. End portions of the P blades, located at the other side in the axial direction, do not substantially extend beyond the end portion of the peripheral wall of the annular member located at the other side in the axial direction.
The housing may be formed as one integral structure but it may also be formed of two or more constitutional parts. For example, when the counter-rotating axial-flow fan of this invention is made by coupling two axial-flow fan units, the housing is constructed by coupling the cases of the two axial-flow fan units.
When a first axial-flow fan unit and a second axial-flow fan unit are coupled together to form the counter-rotating axial-flow fan, the first axial-flow fan unit includes a first case, a first impeller, a first motor and a plurality of webs. The first case includes an air channel having a suction opening portion at one side in an axial direction thereof and a discharge opening portion at the other side in the axial direction. The first impeller includes a plurality of front blades that rotate in the suction opening portion. The first motor rotates the first impeller about the axial line in one of two rotating directions. The plurality of webs are located in the discharge opening portion and disposed at a predetermined interval in a circumferential direction to fix the first motor to the first case. Similarly, the second axial-flow fan unit includes a second case, a second impeller, a second motor and a plurality of webs. The second case includes an air channel having a suction opening portion at one side in an axial direction thereof and a discharge opening portion at the other side in the axial direction. The second impeller includes a plurality of rear blades that rotate in the discharge opening portion. The second motor rotates the second impeller about the axial line in the other rotating direction opposite to the one rotating direction. The plurality of webs are located in the suction opening portion and disposed at a predetermined interval in a circumferential direction to fix the second motor to the second case. The first case of the first axial-flow fan unit and the second case of the second axial-flow fan unit are coupled together to form the housing. In that case, the plurality of webs of the first axial-flow fan unit and the plurality of webs of the second axial-flow fan unit are preferably coupled to form a plurality of radially extending stationary blades arranged stationary in the housing between the first impeller and the second impeller. With this arrangement, there is no need to construct a case having a plurality of stationary blades separately from the axial-flow fan units, reducing the number of parts used in the counter-rotating axial-flow fan. Further, compared with a case where a separate unit having a plurality of stationary blades is used, the counter-rotating axial-flow fan of this invention can be reduced in an axial overall size.
Specifically, in the present invention a length L3 of the first case, measured in the axial direction is defined to be longer than a length 4 of the second case, measured in the axial direction. The lengths L1 and L2 are defined so that a ratio of the two lengths L1/L2 is 1.3 to 2.5. The lengths L3 and L4 are defined so that a ratio of the two lengths L3/L4 is 1.2 to 1.8.
More specifically, the front blades are curved in a transverse cross section of the front blades as taken along a direction parallel to the axial line (or along the axial line) so that their concave portions are open toward the rotating direction of the first impeller, i.e. in the one rotating direction as described above. The rear blades are curved in a transverse cross section of the rear blades as taken along a direction parallel to the axial line so that their concave portions are open toward the rotating direction of the second impeller, i.e. in the other rotating direction as described above. In this construction, the stationary blades are preferably curved in a transverse cross section of the stationary blades as taken along a direction parallel to the axial line so that their concave portions are open toward the other rotating direction (the rotating direction of the second impeller) and toward a direction in which the rear blades are located. With this arrangement, it is possible to increase the maximum amount of air and the maximum static pressure while reducing the suction noise.
More specifically, the first impeller may include an annular member having a peripheral wall surrounding the axial line on which base portions of five front blades are integrally mounted. The second impeller may include an annular member having a peripheral wall surrounding the axial line on which base portions of four rear blades are integrally mounted. This arrangement allows the first and second impellers to be formed easily by resin injection molding.
The rotating speed of the second impeller is preferably set slower than that of the first impeller for reducing noise.
In the counter-rotating axial-flow fan of the present invention, a length L1 of each of the N front blades, measured in the axial direction is set longer than a length L2 of each of the P rear blades, measured in the axial direction. Then the air amount and the static pressure can be increased, compared with conventional fans.
Now, an embodiment of the present invention will be described in detail by referring to
A counter-rotating axial-flow fan of this embodiment is constructed via a coupling structure of the first axial-flow fan unit 1 and the second axial-flow fan unit 2.
The first axial-flow fan unit 1 has a first case 5, a first impeller (front impeller) 7, a first motor 25, and three webs 19, 21, 23 spaced apart 120 degrees circumferentially, all of which are arranged in the first case 5. The first case 5 has an annular suction-side flange 9 at one side in the axial direction in which the axial line A extends and an annular discharge-side flange 11 at the other side. The first case 5 also has a cylindrical portion 13 between the two flanges 9, 11. The flanges 9, 11 and an inner space in the cylindrical portion 13 all together form an air channel.
The discharge flange 11 also has an almost rectangular outline with a circular discharge opening portion 17 formed therein. In the discharge opening portion 17, three radially extending webs 19, 21, 23 are arranged at circumferentially equal intervals. Through the three webs 19, 21, 23, a motor case in which a stator of the first motor 25 is fixed is secured to the first case 5. Of the three webs 19, 21, 23, the web 19 has a groove-shaped recessed portion 19a opening toward the second axial-flow fan unit 3. In this recessed portion 19a is installed a feeder wire not shown which is connected to an excitation winding of the first motor 25. The three webs 19, 21, 23 are respectively combined with three webs 43, 45, 47, described later, of the second axial-flow fan unit 3 to form M stationary blades 61, three in the embodiment, (
The first motor 25 comprises a rotor not shown, to which the first impeller 7 of
The discharge-side flange 11 has flat faces 11a formed at each of four corner portions 12A to 12D facing the cylindrical portion 13. At the four corner portions 12A to 12D are formed four first fitting grooves 29 that constitute engaged portions of a first kind, as shown in
Except for the corner portion 12B adjacent to the web 19 in which a wire not shown is installed, the plurality of corner portions 12A, 12C, 12D are each formed with a second fitting groove 31 that constitutes an engaged portion of a second kind. As shown in
The second axial-flow fan unit 3 has a second case 33, a second impeller (rear impeller) 35 in
The suction-side flange 37 has an almost rectangular outline, with a circular suction opening portion 42 formed therein. In the suction opening portion 42, three radially extending webs 43, 45, 47 are arranged at circumferentially equal intervals. The second motor 49 is secured to the second case 33 through the plurality of webs 43, 45, 47. Of the plurality of webs 43, 45, 47, the web 43 has a groove-shaped recessed portion 43a opening toward the first axial-flow fan unit 1. In this recessed portion 43a is installed a feeder wire not shown which is connected to an excitation winding of the second motor 49. The three webs 43, 45, 47 combine respectively with three webs 19, 21, 23 of the first axial-flow fan unit 1 to form M stationary blades 61 (three in the embodiment) described later.
The second motor 49 comprises a rotor not shown to which the second impeller 35 of
The second impeller 35 has an annular member 50 fitted with a cup-shaped member, not shown, of the rotor which is secured to a shaft, not shown, of the second motor 49, and P rear blades 51 (four in the embodiment) integrally provided on an outer peripheral surface of an annular wall 50a of the annular member 50.
Four corner portions 36A to 36D of the suction-side flange 37 are formed with a through-hole 38 through which a mounting screw passes, as shown in
As shown in
When the number of the front blades 28 is N, that of the stationary blades 61 is M, and that of the rear blades 51 is P, each of N, M and P is a positive integer, and a relationship among N, M and P is defined as N>P>M in the counter-rotating axial-flow fan of the present invention. Since N=5, P=4 and M=3 in this embodiment, the relationship among N, M and P is 5>4>3.
Specifically in the counter-rotating axial-flow fan of the present invention, a length L1, of each the N front blades 28 of the first axial-fan unit 1, measured in an axial direction is set longer than the length L2, of each the P rear blades 51 of the second axial-fan unit 3, measured in the axial direction as shown in
More specifically, end portions 28a of the N front blades 28 of the first axial-fan unit 1, located at the other side in the axial direction (at the discharge opening portion 17), extend toward a direction of the other side (at the discharge opening portion 17) beyond an end portion 27aa of the peripheral wall 27a of the annular member 27, located at the other side in the axial direction (at the discharge opening portion 17). End portions 51b of the rear P blades 51 of the second axial-flow fan unit 3, located at the one side in the axial direction (at the suction opening portion 42), do not substantially extend beyond an end portion 50ab of the peripheral wall 50a of the annular member 50 located at the one side in the axial direction (at the suction opening portion 42). End portions 51a of the rear P blades, located at the other side in the axial direction (at the discharge opening portion 57), do not substantially extend beyond the end portion 50aa of the peripheral wall 50a of the annular member 50 located at the other side in the axial direction (at the discharge opening portion 57).
Each of the end portions 28a, of the N front blades 28, located at the other side (at the discharge opening portion 17) in the axial direction extends beyond the end portion 27aa, of the peripheral wall 27a of the annular member 27, located at the other side (at the discharge opening portion 17) in the axial direction. A length La of an extended part for each of the end portions 28a of the N front blades 28, which extends toward the other side in the axial direction beyond the end portion 27aa of the peripheral wall 27a of the annular member 27 is within a range from 10 percent to 15 percent of the length L1.
A length L3 of the first case 5 measured in the axial direction A is set longer than a length L4 of the second case 3 measured in the axial direction. The length L3 is set longer than the length L4. In this embodiment, the length L3 is set to 30 millimeter and the length L4 is set to 26 millimeter. Preferably the length L3 and the length L4 are determined so that a ratio of the two lengths L3/L4 is a value from 1.2 to 1.8.
In this embodiment of the fan, the first case 5 of the first axial-flow fan unit 1 and the second case 33 of the second axial-flow fan unit 3 are coupled as follows. First, the end portion of the first case 5 and the end portion of the second case 33 are brought close together, and the head portions 53b of the four hooks 53 of the second case 33 are inserted into the corresponding hook passing holes 29a of the four first fitting grooves 29 in the first case 5. At this time, the plurality of protrusions 55 of the second case 33 fit into the openings 31c of the plurality of second fitting grooves 31 in the first case 5. Next, as shown in
In this embodiment, the hooks 53 (engaging portions of first kind) and the first fitting grooves 29 (engaged portions of first kind) are coupled to form an engaging structure of first kind. The protrusions 55 (engaging portions of second kind) and the second fitting grooves 31 (engaged portions of second kind) are coupled to form a second kind of an engaging structure. With this construction, when a separating action to move in the axial direction the first case 5 and the second case 33 out of engagement with each other, the first engaging surfaces 53d of the head portions 53b of the hooks 53 engage with the first engaged surfaces 29d at the flat faces 11a of the discharge-side flange 11, activating the first kind of engaging structure to resist the separating action. Further, when a first rotating action is performed to rotate the first case 5 and the second case 33, in a coupled state, about the axial line A in one rotating direction indicated by arrow D1, the second engaging surfaces 53e of the body portions 53a engage with the second engaged surface 29e of the discharge-side flange 11, activating the first kind of engaging structure to resist the first rotating action. When a second rotating action is performed to rotate the first case 5 and the second case 33, in a coupled state, about the axial line A in a direction indicated by arrow D2, opposite to the one rotating direction (arrow D1), the end faces 55b of the protrusions 55 forming the third engaging surfaces engage with the third engaged surfaces 31e of the engaging grooves 31b of the second fitting grooves 31, activating the second kind of engaging structure to resist the second rotating action. Thus, in the fan of this embodiment, even if the first case 5 and the second case 33 are subjected to a force acting in the direction of arrow D1 or a force acting in the direction of arrow D2, they are prevented from being disconnected.
As shown in
Table 1 shows an actual length L3 of the first case, an actual length L4 of the second case, and a ratio of L3/L4, as well as an actual length L1 of the front blade an actual length L2 of the rear blade, and a ratio of L1/L2, in connection with the characteristics of the amount of wind and a static pressure shown in
As shown most clearly in
In other words, of the present invention, the characteristics of the amount of air and the static pressure can be improved when the length L1 of the front blade is longer than the length L2 of the rear blade. The characteristics of the amount of air and the static pressure will be lowered, when the length L1 of the front blade is too long, while the length of the rear blade is too short.
While a preferred embodiment of the invention has been described with a certain degree of particularity with reference to the drawings, obvious modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
Number | Date | Country | Kind |
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2005-267423 | Sep 2005 | JP | national |
This application is a divisional of U.S. Ser. No. 11/531,510, entitled COUNTER-ROTATING AXIAL-FLOW FAN, filed Sep. 13, 2006 now U.S. Pat. No. 7,445,423.
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Number | Date | Country | |
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Parent | 11531510 | Sep 2006 | US |
Child | 12234921 | US |