JPH05202893A - Air blower - Google Patents

Abstract

PURPOSE:To provide the reduced noise and thickness of a small-sized axial and mixed flow blowers, and. improve pressure characteristics. CONSTITUTION:Because the front edge 8 and the rear edge 8b of a blade 8 are made to be a protruding curve on the downstream side, the meridian sectional shape of the blade 8 declines toward the downstream side around a hub 7, and inclines toward the upstream side at, the chip side when a blade wheel 6 is rotated around a rotating shaft. Because the inclination of the blade 8 is made larger on the chip side where flow rate and centrifugal force are high, the effect of restraining the development, of a border layer becomes large. Besides, because the blade rear edge 8b is formed into the curve with protruding part on the downstream side, the blade rear edge protrudes toward the downstream side from the line linking the hub and the downstream edge of an orifice even when the downstream edge of the orifice 9 is made to meet the downstream edge of the chip. With this constitution, force to send the flow toward the downstream side of the orifice 9 becomes stronger, thus it is possible to improve side of the orifice 9 becomes high load even when the air amount and the low noise are realized by using a thin orifice 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small axial flow or mixed flow blower used for household air conditioners and cooling fans.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional blower of this type has a boss formed at the center of a hub of an impeller 3 provided with a plurality of blades 2 around a substantially cylindrical hub 1. The rotary shaft of the motor 4 is connected and the impeller 3 is surrounded by a substantially cylindrical orifice 5. This feather 2
Various meridional cross-sectional shapes have been devised when rotated around the rotation axis, and in addition to FIG. 3, there are many shapes as shown in FIG. However, in general, the leading edges 2a, 12a, the trailing edge 2
It is usual that both b and 12b are substantially linear. The meridional cross-sectional shape of the blade has a close relationship with the blowing performance, and as shown in FIG. 3, it is possible to reduce the noise mainly by inclining it toward the upstream side of the air flow, that is, by making the angle α in the figure large to some extent. Planned. This is because the flow on the blade surface is caused to flow to the tip side by centrifugal force, the boundary layer develops and separates on the tip side, and causes the noise to make it difficult to flow to the tip side by tilting the blade. It is because it is suppressed by.

The shape of the orifice 5 also has a great influence on the performance. The curved surface shape of the inflow portion, the axial length, the relative position to the impeller, etc. are important parameters for the air volume, wind pressure, and noise performance. Generally, when the axial length of the orifice 5 is increased, the pressure characteristic is improved, but the air volume and the noise characteristic are deteriorated.

[0004]

However, in the above-mentioned conventional configuration, by increasing the inclination angle α of the blade and inclining the blade toward the upstream side, the axial dimension of the impeller becomes large, so that the blade is thin. When a car is required, the blade inclination angle α must be reduced, and a sufficient noise reduction effect cannot be obtained. Further, in general, there is a problem that the static pressure characteristic is deteriorated when the thickness is reduced.

The present invention has been made to solve the above-mentioned problems, and has an object to achieve sufficient noise by achieving a sufficient inclination of the blades toward the upstream side, to achieve a low profile, and to enhance pressure characteristics. is there.

[0006]

In order to achieve the above-mentioned object, the present air blower encloses an impeller having a plurality of blades around a substantially cylindrical hub having a boss portion at the center, and the impeller. An orifice and a motor that is located upstream of the impeller and has a rotation shaft connected to the impeller, wherein the impeller has a meridional cross-sectional shape when rotated around the rotation shaft, a leading edge,
Both trailing edges are composed of curved lines with convex vertices on the downstream side,
The joining point A between the leading edge and the tip is located upstream of the joining point B between the leading edge and the hub, and the joining point C between the trailing edge and the tip is located upstream of the joining point D between the trailing edge and the hub. ,further,
The orifice has a structure in which the axial length of a portion facing the blade is about ½ or less of the axial length of the tip, and the downstream end thereof is provided at substantially the same position as the joint point C.

[0007]

According to the present invention, the meridional cross-sectional shape of the blade when the impeller is rotated about the rotation axis is inclined to the downstream side near the hub and is inclined to the upstream side on the tip side. Therefore, in the impeller having the same axial length, a large inclination can be given to the tip side of the blade. That is, since the blade has a large inclination on the side of the tip having a large flow rate and a large centrifugal force, the effect of suppressing the development of the boundary layer becomes large. Furthermore, since the trailing edge of the blade is composed of a curved line with a convex portion on the downstream side, even when the downstream end of the orifice is aligned with the downstream end of the tip, it is more than the line connecting the hub downstream end and the orifice downstream end. The blade trailing edge projects to the downstream side, and the characteristics under high load are also improved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 6 denotes an impeller, which has a structure in which a plurality of blades 8 are arranged around a substantially cylindrical hub 7. A boss is provided at the center of the hub 7 and is connected to the rotary shaft of the motor 4 placed upstream of the impeller 6.
In the meridional cross-sectional shape of the blade 8 around its axis of rotation, both the leading edge 8a and the trailing edge 8b are composed of curves having convex vertices on the downstream side, and the joining point A between the leading edge 8a and the tip is the leading edge 8a and the hub. Of the trailing edge 8
The junction point C between b and the tip is located upstream of the junction point D between the trailing edge 8b and the hub. Further, the orifice 9 surrounding the impeller 6 has a length (L
o) is set to about 30% or less of the length (Lt) of the tip of the blade, and the downstream end thereof is made to substantially coincide with the joint point C.

FIG. 2 shows the relationship between the inclination angle of the blade and the axial dimension in the above structure in comparison with the conventional example. In the conventional example shown in (a), both the leading edge and the trailing edge of the blade are formed by straight lines, and the inclination angle of the blade is substantially constant. On the other hand, in the impeller of the present invention shown in (b), since the leading edge 8a and the trailing edge 8b are constituted by a curved curve convex toward the downstream side, the blade inclination angle β near the hub
1 is a negative angle. Therefore, even with blades having the same axial dimension, a larger inclination angle β is provided on the outer peripheral side than the convex portions on the front and rear edges.
2 is obtained.

When air is blown by an impeller having such an inclination angle, the effect of the large inclination angle on the tip side of the blade suppresses the phenomenon that the flow on the blade surface flows to the outer peripheral side due to centrifugal force. The effect of controlling the noise due to the separation of the boundary layer can be reduced. On the other hand, on the hub side, the inclination angle of the blades is opposite, so the effect of centrifugal force cannot be suppressed, but on the hub side, the peripheral speed of the blades is originally small, the centrifugal force is weak, and from the middle Since the inclination angle is large, it will not flow further to the outer peripheral side. Moreover, the flow rate itself is considerably larger on the tip side than on the hub side, and the influence on the hub side as a whole is small.

Further, since the trailing edge of the blade is formed by a curved line which is convex toward the downstream side, even when the downstream end of the orifice is set at substantially the same position as the downstream end C of the blade tip, the shaded portion in FIG. The shape of X projects to the downstream side of the orifice. For this reason, the action of sending the flow to the downstream side of the orifice becomes stronger, and a thin orifice whose axial length (Lo) is 1/2 or less of the blade tip length (Lt) is used to reduce the load. Even when the air volume and the low noise are emphasized, there is an effect that the performance under high load can be secured.

[0013]

As described above, in the air blower of the present invention, the leading edge and the trailing edge of the blade are constituted by the curved lines convex toward the downstream side, so that the inclination of the blade can be increased without increasing the axial dimension of the blade. It is possible to increase the angle and reduce noise. In addition, the convex shape of the trailing edge is effective in improving the performance at high load, and in combination with a thin orifice, it is effective in satisfying large air volume and low noise at low load while maintaining performance at high load. There is.

[Brief description of drawings]

FIG. 1 is a sectional view of an air blower according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view comparing an impeller of the blower with a conventional impeller.

FIG. 3 is a sectional view of a conventional blower.

FIG. 4 is a sectional view of another conventional blower.

[Explanation of symbols]

 4 Motor 6 Impeller 7 Hub 8 Blade 8a Leading Edge 8b Trailing Edge 9 Orifice

Claims (1)

[Claims] 1. An impeller in which a plurality of blades are provided around a substantially cylindrical hub having a boss portion in the center, an orifice surrounding the impeller, and an rotary shaft located upstream of the impeller. Includes a motor connected to the impeller, the impeller has a meridional cross-sectional shape when rotated about a rotation axis, the leading edge, the trailing edge is configured with a curve having a convex vertex on the downstream side, The joining point A between the leading edge and the tip is located upstream of the joining point B between the leading edge and the hub, and the joining point C between the trailing edge and the tip is located upstream of the joining point D between the trailing edge and the hub. Furthermore, the blower is such that the axial length of the portion of the orifice facing the blade is less than or equal to 1/2 of the axial length of the tip, and the downstream end of the orifice is at substantially the same position as the junction point C.