Centrifugal type blower unit

Details Centrifugal type blower unit Centrifugal type blower unit

1999-04-05

2001-10-09

Verdier, Christopher (Department: 3745)

Rotary kinetic fluid motors or pumps

Working fluid passage or distributing means associated with...

Casing having tangential inlet or outlet

C415S119000, C415S204000, C415S208100, C415S211100, C415S173600, C416S183000, C416S18600A, C416S189000, C416S192000, C416S22300B

Reexamination Certificate

active

06299409

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application relates to and claims priority from Japanese Patent Application No. Hei.
10-99364
filed on Apr. 10, 1998, and No. Hei. 11-24093 filed on Feb. 1, 1999, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a centrifugal type blower unit which reduces noise generated therefrom without greatly reducing air-blowing capacity. The blower unit is suitable for a vehicle air conditioner.
2. Description of Related Art
In a conventional blower unit, noise (hereinafter referred to as “first noise”) may be generated when air blown from a centrifugal fan collides with a nose portion of a scroll casing. The first noise is approximately proportional to a rotation speed of the centrifugal fan and number of blades of the centrifugal fan. Therefore, in the conventional blower unit, the shape of the nose portion is suitably formed so that the first noise can be decreased.
However, according to an experiment of the inventors of the present invention, noise (hereinafter referred to as “second noise”) having a frequency approximately similar to the first noise is also generated in the conventional blower unit where a filter is disposed at an air suction port of the centrifugal fan. To reduce the second noise, the inventors of the present invention experimentally perform the method for reducing the first noise. However, the second noise cannot be sufficiently reduced by using the method for reducing the first noise.
SUMMARY OF THE INVENTION
To overcome the problems, the inventors of the present invention studied the reason why the second noise is caused. As shown in
FIG. 22
, in a centrifugal fan, air is concentrated to an inner radius side while being whirled, is sucked into an air suction port, and is blown radially outwardly by centrifugal force. However, as shown in
FIG. 22
, because the diameter of the air suction port is made larger than the inner diameter of the centrifugal fan to increase air-blowing amount, air can be sucked from both inner radius side of the centrifugal fan and an end side of blades at a side of the air suction port. Air (i.e., sub-flow air ) sucked from the end side of blades has a small kinetic energy, as compared with air (i.e., main-flow air) sucked from the inner radius side of the centrifugal fan. Therefore, when the sub-flow air is mixed into the main-flow air, unstable whirl may be generated at the end side of the blades. That is, an interference between the sub-flow air and the main-flow air is caused, and the second noise is caused. Thus, the second noise may be generated even though the filter is not provided at the air suction port. For reducing the second noise, a bell-mouth portion forming the air suction port may extend toward a radius inner side to cover the ends of blades. In this case, the second noise is decreased, as shown in FIG.
23
. However, air amount (air capacity) blown by the blower unit is greatly decreased, as the diameter of the air suction port reduces, as shown in FIG.
23
.
In view of the foregoing problems, it is a first object of the present invention to provide a centrifugal type blower unit which reduces second noise generated therefrom without greatly reducing air-blowing capacity.
It is a second object of the present invention to provide a centrifugal type blower unit which can reduce both second noise and low-frequency noise without greatly reducing air-blowing capacity.
According to the present invention, in a centrifugal type blower unit, an air suction port for sucking air from an axial direction of a centrifugal fan has a radius dimension in a radius direction of the centrifugal fan, and the radius dimension of the air suction port is larger than a minimum inner radius dimension of the centrifugal fan in the radius direction. A slanting portion slanted relative to the radius direction by a predetermined slanting angle is formed in each blade of the centrifugal fan in such a manner that an inner radius dimension of the centrifugal fan in the radius direction is increased toward the air suction port. Further, a constant portion connected to the slanting portion is formed in each blade of the centrifugal fan to be approximately parallel to the axial direction. Thus, it can prevent sub-flow air which is sucked into the centrifugal fan from an end side of the blades at the side of the air suction port from interfering with main-flow air. That is, the sub-flow air is sucked into the inner radius side of the centrifugal fan together with main-flow air. As a result, the blower unit can reduce second noise. Further, because the diameter of the air suction port is larger than the minimum inner diameter of the centrifugal fan, it can prevent air-blowing capacity of the blower unit from being decreased. Thus, the blower unit reduces second noise generated therefrom without greatly reducing air-blowing capacity.
Preferably, the slanting angle is in a range of 25°-80°. Therefore, sub-flow air is readily concentrated into the inner radius side of the centrifugal fan together with main-flow air, so that the interference between main-flow air and sub-flow air can be prevented. Thus, the second noise can be readily restricted.
More preferably, a bell-mouth portion for forming the air suction port has a covering member for covering the slanting portion, and the covering member extends to a radius inner side of the centrifugal fan in the radius direction. Therefore, an interference between suction air sucked from the air suction port and back-flow air can be prevented so that low-frequency noise of the blower unit can be decreased, while the second noise of the blower unit is decreased.
Still more preferably, the covering member is formed at a predetermined position corresponding to a noise portion of a scroll casing. Therefore, the blower unit of the present invention can decrease both the second noise and the low-frequency noise without greatly reducing air-blowing capacity.
Further, each of the blades has a first end at a radius inside and a second end at a radius outside of the first end. Each of the blades has a first curvature radius at a side of the first end, and a second curvature radius at a side of the second end. In each blade of the centrifugal fan, the first curvature radius is smaller than the second curvature radius. Thus, consumption power of the blower unit can be decreased, while noise generated from the blower unit is decreased.
Preferably, the first curvature radius is for a first area of each blade, from the first end to about ¼ position of a blade length in the radius direction. Therefore, consumption power of the blower unit can be further decreased, while noise generated from the blower unit is decreased.


REFERENCES:
patent: 4363601 (1982-12-01), Leskinen
patent: 4432964 (1984-02-01), Kuroda et al.
patent: 5813831 (1998-09-01), Matsunaga et al.
patent: 5911751 (1999-06-01), Kim
patent: 5971709 (1999-10-01), Hauser
patent: 2-5-38877 (1993-06-01), None
patent: 5-321891 (1993-12-01), None
patent: 9-126190 (1997-05-01), None

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