JPH0663513B2 - Blower - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impeller for reducing the blowing noise of a centrifugal fan, especially whistle noise.

2. Description of the Related Art A conventional impeller will be described with reference to a turbo centrifugal impeller shown in FIGS. 5 and 6.

A conventional turbo-type centrifugal impeller 10 has a plurality of blades 3 installed between a main plate 1 and a sub-plate 2, and the outer peripheral side 5 of the blade 3 is in the rotational direction of the impeller than the inner peripheral side 4. The centrifugal impeller is rotated with a delay with respect to 6, and a spiral casing 7 is attached to such a centrifugal impeller to blow air.

Here, the air to be blown is sucked from the suction port 9 of the centrifugal impeller, is subjected to centrifugal force by the blades 3 of the centrifugal impeller, is discharged from the outer circumference of the impeller, and is further casing by a spiral casing surrounding the outer circumference. It is guided to the outlet 11 and blown out.

Reference numeral 8 is a casing tongue portion, 12 is a motor shaft, and 13 is an impeller mounting boss.

Problems to be Solved by the Invention In such a configuration, each blade of the centrifugal impeller induces pressure fluctuation by traversing the tongue of the casing, and as a result, NZ proportional to the product of the number of blades and the number of rotations. Sound (whistle)
It was making a sound called. In particular, there has been a problem that the level becomes extremely high as the number of rotations increases.

The present invention solves the above-mentioned conventional problems. By disposing the trailing edge of the blade of the centrifugal impeller at an angle with respect to the rotation axis, the generated energy of sound is dispersed in time, and the whistle is dispersed. The purpose is to suppress the generation of sound.

Means for Solving the Problems The present invention for solving the above problems sandwiches a plurality of blades between a main plate and a sub plate having the same outer diameter, and the blades have a short blade arc on the main plate side. The centrifugal impeller is configured by alternately arranging the cutting blades having the trailing edge of the blades cut and the cutting blades cut so that the blade arc on the side of the secondary plate is shortened.

Operation The present invention can provide a time difference at the time when the outermost trailing edge of the centrifugal impeller and the innermost trailing edge of the centrifugal impeller cross the casing tongue. The pressure fluctuation caused by the rotation of the wings is dispersed over time, and the generated energy of the sound is also dispersed, so that the generation of whistle noise is suppressed. Moreover, since the blades are configured by alternately arranging cutting blades that cut the blade trailing edge so that the blade arcs on the main plate side become shorter, and cutting blades that cut so that the blade arcs on the auxiliary plate side become shorter. The outer diameter of the impeller can be made apparently large, and high air blowing performance can be obtained.

Example Hereinafter, one example of the present invention will be described using a turbo centrifugal impeller.

The centrifugal impeller 20 of the present invention holds a plurality of blades 36, 39 of a turbo centrifugal impeller between a main plate 21 and a sub-plate 22 having the same outer diameter, as shown in FIGS. 1 to 3. The wing is a wing arc on the main plate side
The cutting blade 36 is formed by cutting the trailing edge of the blade so that the length of the blade 35 is shortened, and the cutting blade 39 is cut by turns so that the blade arc 37 on the side of the secondary plate is shortened.

Reference numeral 24 is a motor, 25 is a motor shaft, 26 is an impeller fixing boss, 27 is a fan casing, 28 is a casing suction port, 34 is a blade arc on the auxiliary plate side, and 38 is a blade arc on the main plate side.

In such a configuration, the blade of the centrifugal impeller gradually crosses the casing tongue 29 from the trailing edge of the main plate, and finally the trailing edge of the secondary plate crosses the casing tongue. That is, a time difference can be provided at the time when the trailing edge located on the main plate side and the trailing edge located on the sub plate side cross the casing tongue. Therefore, the pressure fluctuation caused by the blade crossing the casing tongue is dispersed in time, the generated energy of sound is dispersed, and the generation of whistle noise is suppressed.

Further, since the cutting blades 36, 39 are alternately arranged,
When the impeller rotates, it becomes a V-shaped cross section as shown in FIG. 4, and the outer diameter of the impeller apparently becomes larger than it actually is. That is, the cross section of only the cutting blade 36 has a wedge shape, and its outer diameter decreases (da-db). However, by alternately arranging the blades as in the present invention, a V-shaped cross section is formed, and the outer diameter decreases ( da
-Db) / 2, which can reduce the decrease in outer diameter by 50% compared to the wedge shape. It is well known that the outer diameter of the impeller has a great influence on the air blowing performance, and for the above reason, a high air blowing performance is obtained by increasing the outer diameter. da is the outer diameter of the impeller, and db is the outer diameter of the cutting edge side.

Further, since the main plate and the sub plate have the same outer diameter, the air flow does not spread in the rotation axis direction even at the blade trailing edge on the inner peripheral side, and the flow in the impeller radial direction is guided. , High ventilation performance can be obtained. The arrow 33 indicates the direction of air flow.

Effects of the Invention As described above, according to the centrifugal impeller of the present invention, a trailing edge located on the main plate side and a trailing edge located on the sub plate side can be provided with a time difference at the time when the trailing edge crosses the casing tongue portion, Pressure fluctuations caused by the blades crossing the tongue of the casing are dispersed over time, the generated energy of sound is dispersed, and the generation of whistle noise is suppressed. Further, by alternately arranging blades having different cutting directions, it is possible to increase the outer diameter of the impeller during rotation, and thus it is possible to obtain high air blowing performance. Further, since the main plate and the sub plate have the same outer diameter, the air flow does not spread in the rotation axis direction even at the blade trailing edge on the inner peripheral side, and the flow in the impeller radial direction is guided. There is an effect that high air blowing performance can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of an air blower according to an embodiment of the present invention, FIG. 2 is a side sectional view of the air blower, FIG. 3 is a plan sectional view of the air blower, and FIG. FIG. 5 is a perspective view of a conventional blower, and FIG. 6 is a plan view of the blower. 20 …… Centrifugal impeller, 21 …… Main plate, 22 …… Sub plate, 23 ……
Wings, 30 ... trailing edge, 34,35 ... wing edge arc.

Claims (1)

[Claims] 1. A blade having a plurality of blades sandwiched between a main plate and a sub plate having the same outer diameter, said blade having a blade trailing edge cut so that a blade arc on the main plate side is shortened, and a blade on the sub plate side. An air blower having a centrifugal impeller configured by alternately arranging cutting blades cut so that the blade arc is shortened.