AU602816B2 - Impeller of multiblade blower - Google Patents

Description

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AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION Form

(ORIGINAL)

FOR OFFICE USE 60286 Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority$ Related Art: ,7Jiqsdocument ceontains th 7 nmendrm ents made unO..

'ctAlion 49 and is correAL f 01.sf TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.

1006, QAZA KADOMA

KADOMA-SHI

OSAKA

JAPAN

Actual IL.entort 1, Address for Servicer: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

C C r Complete Specification for the invention entitled: IMPELLER OF MULTIBLADE BLOWER.

The following statement is a full description of this invention including the best method of performing it known to me:- 1 BACKGROUND OF THE INVENTION This invention relates to an impeller such as a cross flow fan or sirocco f~an of the type widely used as fans for air conditioners and othe kinds of equipment.

Ordinarily, the construction of a cross flow fan, a kind of multiblade fan is like the one disclosed in Japanese Patent Unexamined Publication No.

60-17296 and Japanese Utility Model Unexamined Publication No. 59-167990.

That is, a cross flow fan has sp-cific features unlike other types of fans whereby the direction in which air flows into the fan and the direction in which air flows out of the fan are generally reverse to each other, as indicated by the arrows in Fig. 6A, and the air flow rate can generally be Increased in proportion to the axial length of the fan. For this reason, cross flow fans have recently come into wide use* A technique of using a specific arrangement ofimpeller blades is known which resides in the fact that, as shown in Fig. 683, impeller blades _a are disposed at pitch angles deterined on the basis of random numbers without any periodicity to reduce audible rotational noise (nz soundo n: rotating speed, zt number of i9- 1blades) Fig. BA shows an ordinary nz sound frequency characteristic, and Fig. 8B shows an nz sound frequency characteristic based on a random pitch arrangement of Japanese Utility Model Publication No. 12959 discloses the construction of a centrifugal fan.

Fig. 7 shows an example of this type of centrifugal fan which has a structure wherein fluid flows into the fan in the radial direction or obliquely at a fan inlet b and flows out in a spreading manner through an outlet c. This structure is suitable for use under high static pressures and high loads. A design in which each blade d is formed with an aerofoil section has also been adopted with a view to improving aerodynamic characteristics and flow rate characteristics* in a cross flow fan, however, air flows between the blades become disturbed if the pitch angles of the blades are varied in an irregular manner, as 20 described above, resulting in a reduction in the flow rate.

A centrifugal fan designed to improve efficiency by forming an aerofoil section of each blade may have a considerably large weight because the t-hckness of the blade is Increased, if, on the other hand,, a hollow blade structure is adopted, the number of manufacture steps is increased accordingly, res~ulting in an increase in the manufacture cost.

2 t~ te SUMMARY OF THiE INVENTION In view of theses problems, an object of the present invention is to provide a low-cost and light weight multiblade fan improved in flow rate characteristics.

To this end, the present invention provides an impeller of a multiblade blower having at least two end Iplates or partition plates spaced apart from each other, and a plurality of blades disposed between said partition plates, each blade having an inner peripheral end and an outer peripheral end, each blade having a cylindrical portion at its respective inner peripheral end and extending substantially along the length of said blade, the diameter of ~rsaid cylindrical portion being larger than the thickness of a portion of said blade connected to said cylindrical portion.

t t This arrangement enables a reduction in the impact t thereby improving the flow rate characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. I is a perspective view of portion of blades of a cross-flow impeller in accordance with an embodiment of the present invention; Figs. 2A and 2B are cross-sectional views of different cross-flow blowexi having the same blades as the impeller shown in Fig. 1; Fig. 3 is a diagram of a flow of air wAith respect to the blade shown in Fig. 1; Fig. 4A is a perspective view of a centrifugal impeller with represents another embodiment of the present invention; J4~i~ A ~7' pop- 1 Fig. 4B is a cross-sectional view of a blower having an impeller of the type shown in Fig. 4A; Fig. 5 is a diagram of comparison between 2 characteristics of the different types of conventional bltower and t' present invention with respect to the relationship between the flow rate and the rotating speed; Fig. 6A is a partially sectioned perspective view of a cross flow blower; Fig. 6B is a cross-sectional view of essential portions of a conventional impeller; and Fig. 7 is a perspective view of an example of another type of conventional impeller partially cut off; is Figs. BA and 8B are diagrams Illustrating ordinary nz-souna frequency characteristics and nz-sound r-requency characteristics relating to a random pitch arrangement of blades, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings.

An oxaniple of application of the present Invention to a cross flow fan will first be described first with specific reference t; rigs, I to 3. The fundamental. structure of a blower having a cross flow tan described herein is the same as the one shown in -1 W I Fig. 6a and described below.

A well-known type of blower illustrated in Fig. 6a has a cross flow fan (hereinafter referred to as "impeller"), a stabilizer 2, a rear guider 3, partition plates 4 disposed at desired intervals, and blades disposed between the partition plates 4.

Referring to Fig. 1, a blade 5 of this embodiment has a cylindrical portion 6 formed at its one end corresponding to the inner peripheral side of the impeller so as to extend in the longitudinal direction of the blade 5. The diameter T of the cylindrical portion 6 is larger than the thickness t of the blade at the corresponding end thereof, as shown In Fig. 3.

The thus-constructed blower may have an arrangement of the blades such as that shown In Fig. 2A in which the blades 5 are disposed with pitches based on random numbers (irregular intervals), or an arrangement such as that shown in rig. 2Bl in which the blades 5 are disposed with equal pitches.

The state of air flows across the region of the blades 5 will be described below with reference to Pig. 3.

In the conventional arrangement# wind-cut noise (aerodynamic noise) or edge tone Is generated at the inlet side when the blades move across air flows, or flow rate characteristics are considerably Impaired due to inflow impact losses.

To cope. with this problemp the cylindrical 1 portion 6 is formed at the inner peripheral end of each blade 5, thereby ensuring that separation can be prevented even though a slight difference exists between the direction in which the air is drawn into the impeller and the direction of the blade inlet angle.

The reduction in the blowing efficiency due to separation and occurrence of noise aea thereby limited.

Fig. 5 shows a graph of comparison between flow rate characteristics of the conventional cross flow blower structure and the present invention as a result j of an experiment.

In Fig. 5, a reference character e designates a fan having blades disposed at random pitch angles, a reference character d a fan having blades disposed at equal pitch angles, and a reference character f the fan in accordance with the present invention having blades disposed at random pitch angles and having circular portions 6 formed on the blades.

As can be understood from Fig. 5, the higher the rotating speed, the lower the flow rate would be in the ordinary random fan in comparison with respect the equal pitch fan.

J! However, the arrangement in accordance with the present invention in which cylindrical portions 6 were formed at the inner peripheral side oE the random fan enabled flow rate characteristics substantially the same as the equal pitch arrangement, thus improving the blowing performance.

6 1. The process and the results of the experiment of these types of fans were as follows.

Specification of fan Diameter of fan: 86 mm Number of blades: 36 Ratio of inside and outside diameters: about 0.79 Thickness of blade edge: about 0.5 mm Diameter of cylindrical portion 6: about I mm Diameter of cylindrical portion 7: about I mm Number of units: 8 Table 1 Rotating spedSound [dB.) rpm Conventional Present rmexample invention 1430 9.77 9185 1200 7.8 7.87 1050 6.56 6.62 875 5.1 5.17

I

Thus, it is possible to improve the glow rate characteristics by forming, on each blade edge at the inner peripheral side of the impeller, the cylindrical portion 6 having a diameter larger than the thickness of the corresponding edge og the blade 5 lengthwise thereog. Each blade can be formed with the desired aerofoil seation while limiting the Increase in the weight and the manufacture cost.

The present Invention can also be applied in -7 .the same manner to a centrifugal blower such as that shown in Figs. 4A and In this arrangement, the impell.er operates in such a manner that air flows into the impeller in the axial direction or obliquely and exits by spreading out in the radial direction as indicated by the arrows in I Fig. 4A, and the impell~er has cylindrical portions formed at inner edges of blades 5. This arrangement is as effective as the example shown in Fig. The Impeller I illustrated in Figs. 4A and 4B has a spiral caFning 2a, a boss 3a, partition plates 4, blades 5 and cylindrical portions 6.

In the first embodiment, the cross-flow fan has a plurality of units separated by the partition plates 4 arranged in the axial direction. it Is of course possible that the present invention enables similar effects when applied to a single unit fan.

As is apparent from the above-described embodiments, in the impeller of the mulbiblade blower In accordance with the present invention, a cylindrical portion is formed on an edge of each of the blades ait the Inner peripheral side of the i-mpeller so as to extend through the overall length omO the blade and to have a diameter larger than! the thickness of the edge of 26 the blade, thereby improving the flow rate characteristics, a

Claims (1)

1. An impeller of a multiblade blower having at least two end plates or partition plates spaced apart from each other, and a plurality of blades disposed between said partition plates, each blade'having an inner peripheral end and an outer peripheral end, each blade having a cylindrical portion at its respective inner peripheral end and extending substantially along the length of said blade, the diameter of said cylindrical portion being larger than the thickness of a portion of said blade connected to said cylindrical portion. DATED THIS 26th DAY OF July 1990 MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD. By Its Patent Attorneys GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia