JPH04194397A - Cross flow fan - Google Patents

Abstract

PURPOSE:To secure such a cross flow fan that is very little in noise by constituting a part equivalent to a supply opening part for a rear guider so as to have a lot of small holes, and installing a sift absorbing material at the outside. CONSTITUTION:A lot of small holes 16 are formed in a supply opening part 15 of a rear guider 13, and thickness of this guider 13 and each diameter and hole rate of these small holes should be set to such valves as determined by each frequency of noises being produced out of a fan, Then, a sound absorbing material 17 made up of soft urethane foam or synthetic rubber foam or the like is installed at the outside of the supply opening part 15. With this constitution, a blade pitch sound generated in and around a stabilizer 14 of the cross flow fan and another sound generated in an impeller 12 due to flowing separation are all absorbed by the small holes 16 installed in the supply opening part of the rear guider 13 and the sound absorbing material 17, thus, any possible noise is reducible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cross-flow fan that is widely used as a blowing device for, for example, an air conditioner.

2. Description of the Related Art A conventional cross flow fan of this type has a configuration as shown in FIG.

That is, a cross-flow type impeller 2 having a large number of blades is disposed between the stabilizer 3 and the rear guider 4 that form the casing, and the stabilizer 3 and the rear guider 4 are connected to each other.
and formed an air outlet 5 to constitute a cross flow fan.

When the impeller 2 rotates, a circulating vortex of air is generated near the stabilizer 3, and a cross flow 6 is induced around the circulating vortex. Due to the structure of the cross-flow fan, this cross-flow 6 becomes a substantially U-turn flow in which the inflow and outflow directions are opposite, or when the entire cross-flow fan is extended in the axial direction, the air volume increases in proportion to its length. In recent years, it has come to be widely used in air conditioners, etc., due to its characteristics such as an increase in

Problems to be Solved by the Invention Among the various devices in which cross flow fans are used,
In particular, there is a remarkable trend toward lower noise levels in air conditioners.

However, the cross-flow fan configured as described above has the problems of higher noise and lower efficiency than other types of blowers. The cause of this is that the stabilizer 3
In the vicinity of the impeller 2, an abnormal sound called a blade pitch sound proportional to the number of blades and the rotation speed of the impeller 2 is generated due to pressure fluctuations caused by the proximity of the stabilizer 3 to the stabilizer 3. Furthermore, even if the suppression angle of the blades 1 is optimized for the flow on the inflow side of the impeller 2, the suppression angle and blade shape will not be suitable on the outflow side, which has rotated approximately 180 degrees, so it cannot be optimized. As a result, both the suction side and the discharge side have a blade shape that would not cause flow separation according to normal blade theory. Therefore, there is a problem in that it is difficult to reduce noise simply by optimizing the blade shape and casing.

The present invention solves these conventional problems and provides a cross flow fan with extremely low noise.

Means for Solving i*a In order to reduce noise, which is a problem of the conventional example, the cross flow fan of the present invention has a large number of small holes formed in the outlet of the rear guider that constitutes the casing. A soft sound-absorbing material is provided on the outside of the rear guider, and the thickness of the rear guider and the diameter and aperture ratio of the small holes are set to values determined by the frequency of noise generated from the fan.

Effect: With the above-described configuration, the present invention uses small holes provided at the outlet of the rear guider to absorb sound such as the blade pinching sound generated near the stabilizer of the cross flow fan and the sound generated by the impeller due to flow separation. The purpose is to reduce noise by absorbing sound with the material.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

As shown in FIGS. 1 and 2, the cross-flow fan of the present invention has a cross-flow type in which a plurality of series 11 each consisting of a large number of blades Lla and an end plate 11b that supports the blades 11a are connected in the axial direction. An impeller 12 is configured. A casing is constituted by a rear guider 13 provided so as to cover one circumferential side of the impeller 12, and a stabilizer 14 disposed close to the other outer circumferential side. Air can be blown by driving it with a prime mover. A large number of small holes 16 are formed in the air outlet portion 15 of the rear guider 13, and the thickness of the rear guider, the diameter of the small holes, and the aperture ratio are determined to reduce noise generated from the fan, as will be described later in FIG. It is set to a value determined by the frequency. Reference numeral 17 designates a sound absorbing material formed of soft urethane foam, synthetic rubber foam, or the like and provided on the outside of the outlet portion 15 of the rear guider 14.

Now, as shown in FIG. 3, the thickness l and the diameter d of the small hole 16 are
, in a sound absorption mechanism in which an air layer with a distance of 11L (sound absorbing material 17) exists behind a perforated plate with a porosity P (corresponding to the outlet 15 of the rear guider 13 in the example), the resonance frequency fo is calculated by the following formula. It is known that it is given by

P 2π L(1+6) Here, C: Sound speed δ: Q, 8d Thickness l of the outlet part 15 of the rear guider 13 and diameter of the small hole 16 so as to obtain a resonance frequency fo that matches the frequency f of the noise. d, the porosity P, and the thickness L of the sound absorbing material 17, it is possible to obtain a sound absorbing mechanism with excellent noise absorbing performance. Note that since the sound absorbing material 17 has a sufficient thickness, it can exhibit good sound absorbing performance even for noises with a frequency of 1000 Hz or higher.

In the above configuration, when the impeller 12 rotates, a circulating vortex is generated near the stabilizer 14, and a cross-sectional airflow 18 is induced around the circulating vortex. When this cross-sectional airflow 18 flows into the impeller 12, if the angle of attack of the blades 11a is optimized with respect to the flow, the work of the blades on the outflow side is greatly reduced, so it cannot be optimized; It does not flow completely along the flow, causing separation, releasing vortices and causing turbulence, which generates noise. Further, near the stabilizer 14, blade pitch noise is generated due to pressure fluctuations due to the proximity of each blade 11a and the stabilizer 14. However, the noise that comes out along with the airflow 18 to the air outlet portion 15 is absorbed by the above-mentioned sound absorption mechanism provided in the rear guider 13, so that noise reduction can be achieved.

Furthermore, when the technical means of the present invention is used in an air conditioner, the air layer of the sound absorbing material 17 produces a heat insulating effect, so there is no fear of condensation forming on the outlet 15 of the rear guider 13.

As described in detail, if the cross-flow fan of the present invention is used, the blade pitch noise generated near the stabilizer and the noise generated in the impeller due to flow separation can be removed by providing the air outlet at the rear guider. The small holes and sound-absorbing material absorb sound, making it possible to provide a quiet blower with low noise.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main parts of a cross-flow fan according to an embodiment of the present invention, FIG. 2 is a sectional view of the main parts of the cross-flow fan, and FIG. 3 is a sectional view of the main parts of the sound absorption mechanism. 4
The figure is a perspective view of essential parts of a conventional crossflow fan. 12... Impeller, 13... Rear guider, 14... Old stabilizer, 15... Air outlet section, 16... Small hole, 17... ...Sound absorbing material. Name of agent: Patent attorney Akira Okaji and two others 12-・
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Claims (2)

[Claims] (1) Comprised of a cross-flow type impeller, a rear guider that covers one circumferential side of the impeller, and a stabilizer provided close to the other circumferential side, and includes a casing having an air outlet. A cross-flow fan in which a portion corresponding to the outlet of the rear guider is configured to have a large number of small holes, and a soft sound-absorbing material is provided on the outside thereof. (2) Claim 1, wherein the thickness of the rear guider and the diameter and aperture ratio of the small holes in the portion corresponding to the outlet of the rear guider are set to values determined by the frequency of noise generated from the fan.
Cross flow fan as described.