TITLE OF THE INVENTION

Diagonal Flow Fan and Air Conditioner Having Same

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a diagonal flow fan mounted in an outdoor unit or an indoor unit of an air conditioner and, in particular but not exclusively, to a lightweight diagonal flow fan having an increased efficiency and an increased capacity. The present invention also relates to an air conditioner having such a diagonal flow fan.

2. Description of the Related Art

Fig. 7 depicts a conventional diagonal flow fan that includes a rotary shaft 13, a boss 14 secured to the rotary shaft 13, and a plurality of blades 11 rigidly secured to or unitarily formed with the boss 14 on an outer periphery thereof. Each blade 11 has a curved leading edge 11a and a curved trailing edge 11b (see, for example, Japanese Patent No. 3608038).

In this conventional diagonal flow fan, however, if an interval between the leading edge 11a and the trailing edge 11b of an adjacent blade is not designed appropriately, a trailing vortex generated from the trailing edge 11b interferes with a blade 11 positioned downstream, thus resulting in an increase in noise. In particular, if a substantial turbulent fluid impinges on the downstream blade 11, sound of rotation of the blades increases considerably, which leads to objectionable noise at specific frequencies (the speed of rotary shaft 13 x the number of blades 11). Also, in a turbulent flow field, the blades 11 cannot act sufficiently to provide an original capacity or a desired pressure increase, thus resulting in a reduction in performance.

Further, because both the leading edge 11a and the trailing edge 11b of each blade 11 are formed into a curve, molding with the use of, for example, a resin is not easy during production of the fan, thus leading to a reduction in productivity.

SUMMARY OF THE INVENTION

The present invention has been developed to overcome the above-described disadvantages.

It is accordingly an objective of the present invention to provide a diagonal flow fan capable of increasing the air blowing performance, reducing noise, and increasing the productivity.

In accomplishing the above and other objectives, the diagonal flow fan according to the present invention includes a rotatably driven hub and a plurality of blades provided around the hub and each having a leading edge and a trailing edge, the leading edge having an angled portion and a radially outer linear leading edge extending radially outwardly from the angled portion substantially in parallel to the trailing edge of one of the blades adjacent thereto, wherein a distance between the leading edge and the trailing edge of the adjacent blade is set greater on a radially outer side than on a hub side.

By this construction, even if air flows leaving the trailing edge of the blade are turbulent, they hardly impinge on another blade positioned downstream thereof. Because a comparatively large distance can be ensured between the blades, particularly in an radially outer region of the fan, no substantial impingement or interference of such air flows occurs, thus making it possible to reduce noise, particularly sound of rotation of the blades. Also, a chord length of the blade on the hub side can be reduced, which in turn improves the air blowing balance of the blade, thus enhancing the air blowing performance. Further, the leading edge and the trailing edge of the adjacent blade extend substantially parallel to each other and, hence, formation of a mold required for manufacturing the fan is easy, and resin molding of the fan can be easily carried out, thus enhancing the productivity.

The trailing edge has an angled portion and a radially outer linear trailing edge extending radially outwardly from the angled portion. This configuration can further reduce noise, particularly sound of rotation of the blades, and facilitate formation of the mold and molding of the fan, thus enhancing the productivity.

The leading edge has a hub side linear leading edge between the hub and the angled portion, and the trailing edge has a hub side linear trailing edge between the hub and the angled portion. The hub side linear leading edge is parallel to the hub side linear trailing edge of the adjacent blade. This configuration can also reduce noise, particularly sound of rotation of the blades, and facilitate formation of the mold and molding of the fan, thus enhancing the productivity.

Also, the hub includes an axial flow portion and a plurality of diagonal flow portions formed with the axial flow portion. The axial flow portion has an outer peripheral surface extending parallel to a rotary shaft inserted in the hub and is positioned between a junction between the leading edge and the hub and a junction between the trailing edge of the adjacent blade and the hub. Each diagonal flow portion has an extension extending downstream from the trailing edge with respect to a direction of rotation of the fan.

In the area of the axial flow portion, a resistance to the air flow is restrained, thereby enhancing the capacity performance. On the other hand, the area of the diagonal flow portion acts to increase the pressure and accordingly enhance the air blowing performance.

The extension preferably has a circumferential length greater than 10mm to stabilize the moldability of the hub and the trailing edge of each blade and enhance the productivity.

The diagonal flow fan having the above-described features can be employed in an air conditioner. The air conditioner of this kind is inexpensive and highly efficient.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objectives and features of the present invention will become more apparent from the following description of a preferred embodiment thereof with reference to the accompanying drawings, throughout which like parts are designated by like reference numerals, and wherein:

Fig. 1 is a schematic sectional view of an outdoor unit of an air conditioner having a diagonal flow fan according to the present invention;

Fig. 2 is a perspective view of the diagonal flow fan of Fig. 1;

Fig. 3 is a front view of the diagonal flow fan of Fig. 1;

Fig. 4 is a side view of the diagonal flow fan of Fig. 1;

Fig. 5 is a front view of another diagonal flow fan according to the present invention;

Fig. 6 is a front view of a further diagonal flow fan according to the present invention; and

Fig. 7 is a perspective view of a conventional diagonal flow fan.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This application is based on an application No. 2010-167974 filed July 27, 2010 in Japan, the content of which is herein expressly incorporated by reference in its entirety.

Fig. 1 is a sectional view of an outdoor unit of an air conditioner having a diagonal flow fan according to the present invention, and Fig. 2 is a perspective view of the diagonal flow fan. Figs. 3 and 4 are a front view and a side view of the diagonal flow fan, respectively.

The outdoor unit of the air conditioner is provided with a body 1 having a suction opening 2 defined therein. The body 1 accommodates a heat exchanger 3, a fan 4, a fan motor 5 for driving the fan 4, and a compressor 8. The compressor 8 is separated from the heat exchanger 3, the fan 4, and the fan motor 5 by a partition plate 9. The partition plate 9 has an orifice or throttled portion 6 unitarily formed therewith so as to encircle the fan 4. The body 1 also has a discharge grille 7 defined therein on a side opposite the suction opening 2. The fan 4 includes a boss or hub 4B generally in the form of a truncated cone and a plurality of (for example, at least three) blades 4A rigidly secured to or unitarily formed with the hub 4B on an outer periphery thereof.

The fan 4 is rotated by driving the fan motor 5, and air induced by the rotation of the fan 4 flows through the heat exchanger 3 via the suction opening 2. The heat exchanger 3 exchanges heat with such air, which in turn flows into the fan 4. The fan 4 increases the speed and pressure of the air, which are maximized in the vicinity of the throttled portion 6. Thereafter, the air passes through the discharge grille 7 and is discharged outside the body 1. An air flow is schematically indicated by arrows in Fig. 1.

As shown in Figs. 2 and 3, each blade 4A has a leading edge 41 positioned on an upstream side thereof with respect to a direction of rotation of the fan 4, a trailing edge 42 positioned on a downstream side of the leading edge 41, and an outer peripheral edge (tip portion) 43 configured to connect the leading edge 41 and the trailing edge 42 to form an outer periphery of the fan 4. The leading edge 41 has an angled portion (depressed portion) Lc, and the trailing edge 42 has an angled portion (protruding portion) Tc. In the front view of Fig. 3 or in a projection view as viewed from the front of the fan 4, a hub side leading edge 41A extending between the angled portion Lc and the hub 4B, and a radially outer leading edge 41B extending radially outwardly from the angled portion Lc are both formed substantially linearly. A hub side trailing edge 42A extending between the angled portion Tc and the hub 4B, and a radially outer trailing edge 42B extending radially outwardly from the angled portion Tc are both similarly formed substantially linearly.

The radially outer leading edge 41B and the radially outer trailing edge 42B of an adjacent blade 4A are spaced a distance A from and substantially parallel to each other. The hub side leading edge 41A and the hub side trailing edge 42A of the adjacent blade 4A are spaced a distance B from and substantially parallel to each other. The distance A is greater than the distance B (A>B).

In this configuration, the angled portion Tc is always positioned on the side of the hub 4B with respect to the angled portion Lc. Accordingly, a chord length of the blade 4A in the vicinity of the hub 4B, which does not work so much, reduces, and a reduction in chord length improves the air blowing balance of the blade 4A, thus enhancing the air blowing performance.

Arrows as shown in Fig. 3 indicate a direction of an air flow discharged from the trailing edge 42 in the vicinity of the outer peripheral edge 43. The air flow in the vicinity of the outer peripheral edge 43 has a strong tendency to flow radially outwardly of the fan 4 due to a centrifugal force created by the rotation of the fan 4, and is spaced a sufficient distance A from the leading edge 41 of the downstream side blade 4A. For this reason, the air flow in the vicinity of the outer peripheral edge 43 does not impinge on or interfere with the downstream side blade 4A after leaving the trailing edge 42, thus not giving rise to an increase of noise caused by the interference and, in particular, an increase of sound of rotation of the blades.

In general, fan blades can provide neither a sufficient capacity nor a sufficient pressure in a turbulent flow field, but the blades 4A of the configuration as described above can provide them and do not lower the air blowing performance. That is, rotation of a blade generally causes a turbulent blade wake (a turbulent flow on a downstream side thereof), which in turn creates a large resistance to a downstream side blade to thereby reduce the speed of the blades. According to the present invention, however, the turbulent blade wake hardly affects any influence on the downstream side blade and, hence, no substantial reduction in speed of the blades occurs.

Further, because the radially outer leading edge 41B and the radially outer trailing edge 42B of an adjacent blade 4A extend substantially parallel to each other, and because the hub side leading edge 41A and the hub side trailing edge 42A of the adjacent blade 4A similarly extend substantially parallel to each other, formation of a mold required for manufacturing the fan 4 is easy, and molding of the fan 4 can be easily carried out, thus enhancing the productivity.

As shown in Figs. 2 to 4, the hub 4B is made up of an axial flow portion (cylindrical portion) Ha and a plurality of diagonal flow portions (frusto-conical portions) Hm unitarily formed with the axial flow portion Ha. The axial flow portion Ha has an outer peripheral surface extending parallel to a rotary shaft that is to be inserted into the hub 4B. As viewed from the front of the fan 4, the axial flow portion Ha is positioned between a junction between the leading edge 41 and the hub 4B and a junction between the trailing edge 42 of a blade 4A adjacent thereto and the hub 4B. Each diagonal flow portion Hm has an extension (diagonal flow extension) HC extending a length C downstream from the trailing edge 42 of a corresponding one of the blades 4A with respect to the direction of rotation of the fan 4. That is, the extension HC of the diagonal flow portion Hm forms a stepped portion on the axial flow portion Ha. In terms of stabilized moldability or formability of the hub 4B and the trailing edge 42 of each blade 4A and in terms of enhanced productivity, it is preferred that the circumferential length C of the extension HC of the diagonal flow portion Hm be greater than 10mm.

In the area of the axial flow portion Ha, a resistance to the air flow is restrained, thereby enhancing the capacity performance. Although the junction between the leading edge 41 and the hub 4B is positioned on the axial flow portion Ha, a junction between the entire blade 4A and the hub 4B is positioned on the diagonal flow portion Hm. The area of the diagonal flow portion Hm acts to increase the pressure.

The hub 4B according to the present invention has both the advantage of the axial flow portion Ha capable of restraining the resistance to the air flow and increasing the weight performance and the advantage of the diagonal flow portion Hm capable of increasing the pressure.

It is to be noted here that the outer peripheral surface of each diagonal flow portion Hm is not always part of a frustum of a cone having an axial centerline coincident with that of the rotary shaft of the hub 4B.

As described above, according to the present invention, each of the hub side leading edge 41 A, the radially outer leading edge 41B, the hub side trailing edge 42A, and the radially outer trailing edge 42B is substantially linearly formed. Also, the hub side leading edge 41A and the hub side trailing edge 42A of an adjacent blade 4A are substantially parallel to each other, the radially outer leading edge 41B and the radially outer trailing edge 42B of the adjacent blade 4A are similarly substantially parallel to each other, and the distance A is greater than the distance B. However, the configuration of the fan 4 is not limited to the configuration as set forth above, and similar effects can be obtained by a configuration in which at least the hub side leading edge 41A and part of the trailing edge 42 are substantially parallel to each other, and the distance between the leading edge 41 and the trailing edge 42 is set such that the distance A on the radially outer side is greater than the distance B on the hub side.

By way of example, as shown in Fig. 5, the trailing edge 42 need not have an angled portion Tc. In the case of Fig. 5, the entire trailing edge 42 is substantially linearly formed and extends substantially parallel to the radially outer leading edge 41b extending substantially linearly, and the distance A on the radially outer side is set greater than the distance B on the hub side.

Alternatively, as shown in Fig. 6, the hub side leading edge 41A does not have to be linearly formed, but may be formed into a curve. Similarly, the hub side trailing edge 42A does not have to be linearly formed, but may be formed into a curve.

The diagonal flow fan according to the present invention can be mounted in an outdoor unit of an air conditioner and is also applicable to any other machines for utilization of the effects thereof. In particular, the diagonal flow fan according to the present invention can increase the air blowing performance such as the capacity and the pressure, can reduce noise, and facilitates production of a mold and molding with the use of, for example, a resin, thus leading to an increase in productivity. Accordingly, the diagonal flow fan according to the present invention is effectively applied to machines requiring a high-performance fan at a low cost.

Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications otherwise depart from the spirit and scope of the present invention, they should be construed as being included therein.

What is claimed is:

1. A diagonal flow fan comprising:

a rotatably driven hub;

a plurality of blades provided around the hub and each having a leading edge and a trailing edge; and

the leading edge having an angled portion and a radially outer linear leading edge extending radially outwardly from the angled portion substantially in parallel to the trailing edge of one of the blades adjacent thereto;

wherein a distance between the leading edge and the trailing edge of the adjacent blade is set greater on a radially outer side than on a hub side.

2. The diagonal flow fan according to claim 1, wherein the trailing edge has an angled portion and a radially outer linear trailing edge extending radially outwardly from the angled portion.

3. The diagonal flow fan according to claim 1, wherein the leading edge has a hub side linear leading edge between the hub and the angled portion, and the trailing edge has a hub side linear trailing edge between the hub and the angled portion, and wherein the hub side linear leading edge is parallel to the hub side linear trailing edge of the adjacent blade.

4. The diagonal flow fan according to any one of claims 1 to 3, further comprising a rotary shaft inserted into the hub, wherein the hub comprises an axial flow portion and a plurality of diagonal flow portions formed with the axial flow portion, the axial flow portion having an outer peripheral surface extending parallel to the rotary shaft and being positioned between a junction between the leading edge and the hub and a junction between the trailing edge of the adjacent blade and the hub, each diagonal flow portion having an extension extending downstream from the trailing edge with respect to a direction of rotation of the fan.

5. The diagonal flow fan according to claim 4, wherein the extension has a circumferential length greater than 10mm.

6. An air conditioner comprising the diagonal flow fan according to any one of claims 1 to 5.